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I have a VAE architecture script as follows:
import numpy as np
import tensorflow as tf
from tensorflow.keras.layers import Input, Conv2D, Flatten, Dense, Conv2DTranspose, Lambda, Reshape, Layer
from tensorflow.keras.models import Model
from tensorflow.keras.optimizers import Adam
from tensorflow.keras import backend as K
INPUT_DIM = (64,64,3)
CONV_FILTERS = [32,64,64, 128]
CONV_KERNEL_SIZES = [4,4,4,4]
CONV_STRIDES = [2,2,2,2]
CONV_ACTIVATIONS = ['relu','relu','relu','relu']
DENSE_SIZE = 1024
CONV_T_FILTERS = [64,64,32,3]
CONV_T_KERNEL_SIZES = [5,5,6,6]
CONV_T_STRIDES = [2,2,2,2]
CONV_T_ACTIVATIONS = ['relu','relu','relu','sigmoid']
Z_DIM = 32
BATCH_SIZE = 100
LEARNING_RATE = 0.0001
KL_TOLERANCE = 0.5
class Sampling(Layer):
def call(self, inputs):
mu, log_var = inputs
epsilon = K.random_normal(shape=K.shape(mu), mean=0., stddev=1.)
return mu + K.exp(log_var / 2) * epsilon
class VAEModel(Model):
def __init__(self, encoder, decoder, r_loss_factor, **kwargs):
super(VAEModel, self).__init__(**kwargs)
self.encoder = encoder
self.decoder = decoder
self.r_loss_factor = r_loss_factor
def train_step(self, data):
if isinstance(data, tuple):
data = data[0]
def compute_kernel(x, y):
x_size = tf.shape(x)[0]
y_size = tf.shape(y)[0]
dim = tf.shape(x)[1]
tiled_x = tf.tile(tf.reshape(x, tf.stack([x_size, 1, dim])), tf.stack([1, y_size, 1]))
tiled_y = tf.tile(tf.reshape(y, tf.stack([1, y_size, dim])), tf.stack([x_size, 1, 1]))
return tf.exp(-tf.reduce_mean(tf.square(tiled_x - tiled_y), axis=2) / tf.cast(dim, tf.float32))
def compute_mmd(x, y):
x_kernel = compute_kernel(x, x)
y_kernel = compute_kernel(y, y)
xy_kernel = compute_kernel(x, y)
return tf.reduce_mean(x_kernel) + tf.reduce_mean(y_kernel) - 2 * tf.reduce_mean(xy_kernel)
with tf.GradientTape() as tape:
z_mean, z_log_var, z = self.encoder(data)
reconstruction = self.decoder(z)
reconstruction_loss = tf.reduce_mean(
tf.square(data - reconstruction), axis = [1,2,3]
)
reconstruction_loss *= self.r_loss_factor
kl_loss = 1 + z_log_var - tf.square(z_mean) - tf.exp(z_log_var)
kl_loss = tf.reduce_sum(kl_loss, axis = 1)
kl_loss *= -0.5
true_samples = tf.random.normal(tf.stack([BATCH_SIZE, Z_DIM]))
loss_mmd = compute_mmd(true_samples, z)
total_loss = reconstruction_loss + loss_mmd
grads = tape.gradient(total_loss, self.trainable_weights)
self.optimizer.apply_gradients(zip(grads, self.trainable_weights))
return {
"loss": total_loss,
"reconstruction_loss": reconstruction_loss,
"kl_loss": kl_loss,
"mmd_loss": loss_mmd
}
def call(self,inputs):
latent = self.encoder(inputs)
return self.decoder(latent)
class VAE():
def __init__(self):
self.models = self._build()
self.full_model = self.models[0]
self.encoder = self.models[1]
self.decoder = self.models[2]
self.input_dim = INPUT_DIM
self.z_dim = Z_DIM
self.learning_rate = LEARNING_RATE
self.kl_tolerance = KL_TOLERANCE
def _build(self):
vae_x = Input(shape=INPUT_DIM, name='observation_input')
vae_c1 = Conv2D(filters = CONV_FILTERS[0], kernel_size = CONV_KERNEL_SIZES[0], strides = CONV_STRIDES[0], activation=CONV_ACTIVATIONS[0], name='conv_layer_1')(vae_x)
vae_c2 = Conv2D(filters = CONV_FILTERS[1], kernel_size = CONV_KERNEL_SIZES[1], strides = CONV_STRIDES[1], activation=CONV_ACTIVATIONS[0], name='conv_layer_2')(vae_c1)
vae_c3= Conv2D(filters = CONV_FILTERS[2], kernel_size = CONV_KERNEL_SIZES[2], strides = CONV_STRIDES[2], activation=CONV_ACTIVATIONS[0], name='conv_layer_3')(vae_c2)
vae_c4= Conv2D(filters = CONV_FILTERS[3], kernel_size = CONV_KERNEL_SIZES[3], strides = CONV_STRIDES[3], activation=CONV_ACTIVATIONS[0], name='conv_layer_4')(vae_c3)
vae_z_in = Flatten()(vae_c4)
vae_z_mean = Dense(Z_DIM, name='mu')(vae_z_in)
vae_z_log_var = Dense(Z_DIM, name='log_var')(vae_z_in)
vae_z = Sampling(name='z')([vae_z_mean, vae_z_log_var])
#### DECODER:
vae_z_input = Input(shape=(Z_DIM,), name='z_input')
vae_dense = Dense(1024, name='dense_layer')(vae_z_input)
vae_unflatten = Reshape((1,1,DENSE_SIZE), name='unflatten')(vae_dense)
vae_d1 = Conv2DTranspose(filters = CONV_T_FILTERS[0], kernel_size = CONV_T_KERNEL_SIZES[0] , strides = CONV_T_STRIDES[0], activation=CONV_T_ACTIVATIONS[0], name='deconv_layer_1')(vae_unflatten)
vae_d2 = Conv2DTranspose(filters = CONV_T_FILTERS[1], kernel_size = CONV_T_KERNEL_SIZES[1] , strides = CONV_T_STRIDES[1], activation=CONV_T_ACTIVATIONS[1], name='deconv_layer_2')(vae_d1)
vae_d3 = Conv2DTranspose(filters = CONV_T_FILTERS[2], kernel_size = CONV_T_KERNEL_SIZES[2] , strides = CONV_T_STRIDES[2], activation=CONV_T_ACTIVATIONS[2], name='deconv_layer_3')(vae_d2)
vae_d4 = Conv2DTranspose(filters = CONV_T_FILTERS[3], kernel_size = CONV_T_KERNEL_SIZES[3] , strides = CONV_T_STRIDES[3], activation=CONV_T_ACTIVATIONS[3], name='deconv_layer_4')(vae_d3)
#### MODELS
vae_encoder = Model(vae_x, [vae_z_mean, vae_z_log_var, vae_z], name = 'encoder')
vae_decoder = Model(vae_z_input, vae_d4, name = 'decoder')
vae_full = VAEModel(vae_encoder, vae_decoder, 10000)
opti = Adam(lr=LEARNING_RATE)
vae_full.compile(optimizer=opti)
return (vae_full,vae_encoder, vae_decoder)
def set_weights(self, filepath):
self.full_model.load_weights(filepath)
def train(self, data):
self.full_model.fit(data, data,
shuffle=True,
epochs=1,
batch_size=BATCH_SIZE)
def save_weights(self, filepath):
self.full_model.save_weights(filepath)
Problem:
vae = VAE()
vae.set_weights(filepath)
throws:
File
"/usr/local/lib/python3.6/dist-packages/tensorflow/python/keras/engine/training.py",
line 2200, in load_weights
'Unable to load weights saved in HDF5 format into a subclassed ' ValueError: Unable to load weights saved in HDF5 format into a
subclassed Model which has not created its variables yet. Call the
Model first, then load the weights.
I am not sure what this means since I am not that proficient in OOP. The surprising bit is that the above code was working until it stopped working. The model is training from scratch and it saves the weights in filepath. But when I am loading the same weights now it is throwing the above error!
If you set model.built = True prior to loading the model weights it works.
i was getting same same error while loading weights via
model.load_weights("Detection_model.h5")
ValueError: Unable to load weights saved in HDF5 format into a subclassed Model which has not created its variables yet. Call the Model first, then load the weights.
solved it by building model before loading weights
model.build(input_shape = <INPUT_SHAPE>)
model.load_weights("Detection_model.h5")
ps, tensorflow Version: 2.5.0
What version of TF are you running? For a while the default saving format was hdf5, but this format cannot support subclassed models as easily, so you get this error. It may be solvable by first training it on a single batch and then loading the weights (to determine how the parts are connected, which is not saved in hdf5).
In the future I would recommend making sure that all saves are done with the TF file format though, it will save you from extra work.
As alwaysmvp45 pointed out "hdf5 does not store how the layers are connected". To make these layers be connected, another way is that you call the model to predict a zeros array with input shape ((1,w,h,c)) before loading weights:
model(np.zeros((1,w,h,c)))
Not sure if this has changed in more recent versions (I'm on 2.4). but I had to go this route:
# Do all the build and training
# ...
# Save the weights
model.save('path/to/location.h5')
# delete any reference to the model
del model
# Now do the load for testing
from tensorflow import keras
model = keras.models.load_model('path/to/location.h5')
If I tried the other suggestions, I got warnings about the layers not being present and I had to build the same model that I did the training on. No big deal, stick it in in a function somewhere, but this works better for me.
I'm working on a project (my first AI project) and I've hit a bit of a wall. When performing testing on my trained classifier, it's predicting that everything is of class 1. Now the data set is heavily biased to class 1; however, I've implemented weights to compensate for this. Just concerned that I've coded this wrong or missed something. Please let me know if you see anything.
This is the setup and training
batchSize = 50
trainingLoad = DataLoader(trainingData, shuffle = True, batch_size = batchSize, drop_last=True)
validationLoad = DataLoader(validationData, shuffle = True, batch_size = batchSize, drop_last=True)
testingLoad = DataLoader(testingData, shuffle = True, batch_size = batchSize, drop_last=True)
vocabularySize = len(wordToNoDict)
output = 3
embedding = 400
hiddenDimension = 524
layers = 4
classifierModel = Classifier.HateSpeechDetector(device, vocabularySize, output, embedding, hiddenDimension, layers)
classifierModel.to(device)
path = 'Program\data\state_dict2.pt'
weights = torch.tensor([1203/1203, 1203/15389, 1203/3407])
criterion = nn.CrossEntropyLoss(weight = weights)
trainClassifier(classifierModel, trainingLoad, validationLoad, device, batchSize, criterion, path)
test(classifierModel, path, testingLoad, batchSize, device, criterion)
def trainClassifier(model, trainingData, validationData, device, batchSize, criterion, path):
epochs = 5
counter = 0
testWithValiEvery = 10
clip = 5
valid_loss_min = np.Inf
lr=0.0001
optimizer = torch.optim.Adam(model.parameters(), lr=lr)
model.train()
for i in range(epochs):
h = model.init_hidden(batchSize, device)
for inputs, labels in trainingData:
h = tuple([e.data for e in h])
inputs, labels = inputs.to(device), labels.to(device)
model.zero_grad()
output, h = model(inputs, h)
loss = criterion(output.squeeze(), labels.long())
loss.backward()
nn.utils.clip_grad_norm_(model.parameters(), clip)
optimizer.step()
counter += 1
print(counter)
if counter%testWithValiEvery == 0:
print("validating")
val_h = model.init_hidden(batchSize, device)
val_losses = []
model.eval()
for inp, lab in validationData:
val_h = tuple([each.data for each in val_h])
inp, lab = inp.to(device), lab.to(device)
out, val_h = model(inp, val_h)#
val_loss = criterion(out.squeeze(), lab.long())
val_losses.append(val_loss.item())
model.train()
print("Epoch: {}/{}...".format(i+1, epochs),
"Step: {}...".format(counter),
"Loss: {:.6f}...".format(loss.item()),
"Val Loss: {:.6f}".format(np.mean(val_losses)))
if np.mean(val_losses) <= valid_loss_min:
torch.save(model.state_dict(), path)
print('Validation loss decreased ({:.6f} --> {:.6f}). Saving model ...'.format(valid_loss_min,np.mean(val_losses)))
print('model saved')
valid_loss_min = np.mean(val_losses)
This is the classifier - Fair amount of random commenting here where i've meddled with bits
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as op
import torchvision
from torch.utils.data import TensorDataset, DataLoader
from torchvision import transforms, datasets
class HateSpeechDetector(nn.Module):
def __init__(self, device, vocabularySize, output, embedding, hidden, layers, dropProb=0.5):
super(HateSpeechDetector, self).__init__()
#Number of outputs (Classes/Categories)
self.output = output
#Number of layers in the LSTM
self.numLayers = layers
#Number of hidden neurons in each LSTM layer
self.hiddenDimensions = hidden
#Device being used for by model (CPU or GPU)
self.device = device
#Embedding layer finds correlations in words by converting word integers into vectors
self.embedding = nn.Embedding(vocabularySize, embedding)
#LSTM stores important data in memory, using it to help with future predictions
self.lstm = nn.LSTM(embedding,hidden,layers,dropout=dropProb,batch_first=True)
#Dropout is used to randomly drop nodes. This helps to prevent overfitting of the model during training
self.dropout = nn.Dropout(dropProb)
#Establishing 4 simple layers and a sigmoid output
self.fc = nn.Linear(hidden, hidden)
self.fc2 = nn.Linear(hidden, hidden)
self.fc3 = nn.Linear(hidden, hidden)
self.fc4 = nn.Linear(hidden, hidden)
self.fc5 = nn.Linear(hidden, hidden)
self.fc6 = nn.Linear(hidden, output)
self.softmax = nn.Softmax(dim=2)
def forward(self, x, hidden):
batchSize = x.size(0)
x = x.long()
embeds = self.embedding(x)
lstm_out, hidden = self.lstm(embeds, hidden)
#Tensor changes here from 250,33,524 to 8250,524
# lstm_out = lstm_out.contiguous().view(-1,self.hiddenDimensions)
out = self.dropout(lstm_out)
out = self.fc(out)
out = self.fc2(out)
out = self.fc3(out)
out = self.fc4(out)
out = self.fc5(out)
out = self.fc6(out)
out = self.softmax(out)
out = out[:,-1,:]
# myTensor = torch.Tensor([0,0,0])
# newOut = torch.zeros(batchSize, self.output)
# count = 0
# row = 0
# for tensor in out:
# if(count == 33):
# newOut[row] = myTensor/33
# myTensor = torch.Tensor([0,0,0])
# row += 1
# count = 0
# myTensor += tensor
# count += 1
return out, hidden
def init_hidden(self, batchSize, device):
weight = next(self.parameters()).data
hidden = (weight.new(self.numLayers, batchSize, self.hiddenDimensions).zero_().to(device), weight.new(self.numLayers, batchSize, self.hiddenDimensions).zero_().to(device))
return hidden
You've added weights to the cross-entropy loss, and the weights bias towards the first class already ([1.0, 0.08, 0.35]).
Having a higher weight for a certain class means that the model will be more heavily penalized for getting that class wrong, and it's possible for the model to learn to just predict everything as the class with highest weight. Usually you don't need to manually assign weights.
Also, check your data to see if there's label imbalance, i.e., whether you have more training examples that are of the first class. An imbalanced training set has similar effects as setting different weights on the loss.
I am training two sub-models in parallel, and want to average them after both of them are finished.
The model is implemented out of tensor2tensor (but still use tensorflow). Part of the definition is like this:
def build_model(self):
layer_sizes = [n,n,n]
kernel_sizes = [n,n,n]
tf.reset_default_graph()
self.graph = tf.Graph()
with self.graph.as_default():
self.num_classes = num_classes
# placeholder for parameter
self.learning_rate = tf.placeholder(tf.float32, name="learning_rate")
self.dropout_keep_prob = tf.placeholder(tf.float32, name="dropout_keep_prob")
self.phase = tf.placeholder(tf.bool, name="phase")
# Placeholders for regular data
self.input_x = tf.placeholder(tf.float32, [None, None, input_feature_dim], name="input_x")
self.input_y = tf.placeholder(tf.float32, [None, num_classes], name="input_y")
h = self.input_x
......[remaining codes]
I save it following:
def save_model(sess, output):
saver = tf.train.Saver()
save_path = saver.save(sess, os.path.join(output, 'model'))
When I load it, I use:
def load_model(self, sess, input_dir, logger):
if logger is not None:
logger.info("Start loading graph ...")
saver = tf.train.import_meta_graph(os.path.join(input_dir, 'model.meta'))
saver.restore(sess, os.path.join(input_dir, 'model'))
self.graph = sess.graph
self.input_x = self.graph.get_tensor_by_name("input_x:0")
self.input_y = self.graph.get_tensor_by_name("input_y:0")
self.num_classes = self.input_y.shape[1]
self.learning_rate = self.graph.get_tensor_by_name("learning_rate:0")
self.dropout_keep_prob = self.graph.get_tensor_by_name("dropout_keep_prob:0")
self.phase = self.graph.get_tensor_by_name("phase:0")
self.loss = self.graph.get_tensor_by_name("loss:0")
self.optimizer = self.graph.get_operation_by_name("optimizer")
self.accuracy = self.graph.get_tensor_by_name("accuracy/accuracy:0")
I use the avg_checkpoint to average two sub-models:
python utils/avg_checkpoints.py
--checkpoints path/to/checkpoint1,path/to/checkpoint2
--num_last_checkpoints 2
--output_path where/to/save/the/output
But I find problems when I check the avg_checkpoints code further:
for checkpoint in checkpoints:
reader = tf.train.load_checkpoint(checkpoint)
for name in var_values:
tensor = reader.get_tensor(name)
var_dtypes[name] = tensor.dtype
var_values[name] += tensor
tf.logging.info("Read from checkpoint %s", checkpoint)
for name in var_values: # Average.
var_values[name] /= len(checkpoints)
with tf.variable_scope(tf.get_variable_scope(), reuse=tf.AUTO_REUSE):
tf_vars = [
tf.get_variable(v, shape=var_values[v].shape, dtype=var_dtypes[v])
for v in var_values
]
placeholders = [tf.placeholder(v.dtype, shape=v.shape) for v in tf_vars]
assign_ops = [tf.assign(v, p) for (v, p) in zip(tf_vars, placeholders)]
global_step = tf.Variable(
0, name="global_step", trainable=False, dtype=tf.int64)
saver = tf.train.Saver(tf.all_variables())
# Build a model consisting only of variables, set them to the average values.
with tf.Session() as sess:
for p, assign_op, (name, value) in zip(placeholders, assign_ops,
six.iteritems(var_values)):
sess.run(assign_op, {p: value})
# Use the built saver to save the averaged checkpoint.
saver.save(sess, FLAGS.output_path, global_step=global_step)
It only save the variables, not all tensors. E.G. when I load it using the above load_model function, it cannot have "input_x:0" tensor. Is this script wrong, or I should modify it based on my use?
I am using TF r1.13. Thanks!
How to add training data(text, melspectrogram, label(.wav)) in Tensorflow 2.0 like tutorials on Tensorflow website?
How to train that model with gradient tape in tf 2.0? I don't know what is the next step to do? I have built the model with layers with tf.keras.layers and tf.sequence_mask. I am replicating deep voice 3 model to do TTS.
def model():
def __init__(self):
with tf.GradientTape() as tape:
self.char2idx, self.idx2char = load_vocab()
self.x, self.y1, self.y2, self.z, self.num_batch = get_batch()
self.prev_max_attentions_li = tf.ones(shape=(hp.dec_layers, hp.batch_size), dtype=tf.int32)
self.decoder_input = tf.concat((tf.zeros_like(self.y1[:, :1, -hp.n_mels:]), self.y1[:, :-1, -hp.n_mels:]), 1)
self.keys, self.vals = Encoder(self.x)
self.mel_logits, self.done_output, self.decoder_output, self.alignments_li, self.max_attentions_li = Decoder(self.decoder_input, self.keys, self.vals, self.prev_max_attentions_li)
self.mel_output = tf.nn.sigmoid(self.mel_logits)
self.converter_input = tf.reshape(self.decoder_output, (-1, hp.Ty, hp.char_embed//hp.r))
self.converter_input = tf.keras.layers.Dense(hp.cchannel, activation = 'relu')(self.converter_input)
self.mag_logits = Converter(self.converter_input)
self.mag_output = tf.nn.sigmoid(self.mag_logits)
self.global_step = tf.Variable(0, name='global_step', trainable=False)
self.loss_mels = tf.reduce_mean(input_tensor=tf.abs(self.mel_output - self.y1))
self.loss_dones = tf.reduce_mean(input_tensor=tf.nn.sparse_softmax_cross_entropy_with_logits(logits=self.done_output, labels=self.y2))
self.loss_mags = tf.reduce_mean(input_tensor=tf.abs(self.mag_output - self.z))
self.loss = self.loss_mels + self.loss_dones + self.loss_mags
# Training Scheme
self.optimizer = tf.keras.optimizer.Adam(lr=hp.lr)
## gradient clipping
self.gvs = self.optimizer.compute_gradients(self.loss)
self.clipped = []
for grad, var in self.gvs:
grad = tf.clip_by_value(grad, -1. * hp.max_grad_val, hp.max_grad_val)
grad = tf.clip_by_norm(grad, hp.max_grad_norm)
self.clipped.append((grad, var))
self.train_op = self.optimizer.apply_gradients(self.clipped, global_step=self.global_step)
# Summary
tf.summary.scalar('Train_Loss/LOSS', self.loss)
tf.summary.scalar('Train_Loss/mels', self.loss_mels)
tf.summary.scalar('Train_Loss/dones', self.loss_dones)
tf.summary.scalar('Train_Loss/mags', self.loss_mags)
self.merged = tf.summary.merge_all()
So I wrote this generalised TensorFlow code and want to save and restore models. But apparently the error is that there is no variables to save. I did everything as given in this official example. Ignore the __init__ method except the last line, since it only takes relevant parameters to train the model with, also there is no Syntax Errors. The error it produces is given below the code.
class Neural_Network(object):
def __init__(self, numberOfLayers, nodes, activations, learningRate,
optimiser = 'GradientDescent', regularizer = None,
dropout = 0.5, initializer = tf.contrib.layers.xavier_initializer()):
self.numberOfLayers = numberOfLayers
self.nodes = nodes
self.activations = activations
self.learningRate = learningRate
self.regularizer = regularizer
self.dropout = dropout
self.initializer = initializer
if(optimiser == 'GradientDescent'):
self.optimiser = tf.train.GradientDescentOptimizer(self.learningRate)
elif(optimiser == 'AdamOptimiser'):
self.optimiser = tf.train.AdamOptimizer(self.learningRate)
self.saver = tf.train.Saver()
def create_Neural_Net(self, numberOfFeatures):
self.numberOfFeatures = numberOfFeatures
self.X = tf.placeholder(dtype = tf.float32, shape = (None, self.numberOfFeatures), name = 'Input_Dataset')
#self.output = None
for i in range(0, self.numberOfLayers):
if(i == 0):
layer = tf.contrib.layers.fully_connected(self.X, self.nodes[i],
activation_fn = self.activations[i],
weights_initializer = self.initializer,
biases_initializer = self.initializer)
elif(i == self.numberOfLayers-1):
self.output = tf.contrib.layers.fully_connected(layer, self.nodes[i],
activation_fn = self.activations[i],
weights_initializer = self.initializer,
biases_initializer = self.initializer)
else:
layer = tf.contrib.layers.fully_connected(layer, self.nodes[i],
activation_fn = self.activations[i],
weights_initializer = self.initializer,
biases_initializer = self.initializer)
def train_Neural_Net(self, dataset, labels, epochs):
entropy = tf.nn.softmax_cross_entropy_with_logits_v2(logits = self.output, labels = labels, name = 'cross_entropy')
loss = tf.reduce_mean(entropy, name = 'loss')
hypothesis = tf.nn.softmax(self.output)
correct_preds = tf.equal(tf.argmax(hypothesis, 1), tf.argmax(labels, 1))
accuracy = tf.reduce_sum(tf.cast(correct_preds, tf.float32))
train_op = self.optimiser.minimize(loss)
self.loss=[]
self.accuracy = []
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
for i in range(0, epochs):
_, l, acc = sess.run([train_op, loss, accuracy], feed_dict = {self.X:dataset})
print('Loss in epoch ' + str(i) + ' is: ' + str(l))
self.loss.append(l)
self.accuracy.append(acc)
self.saver.save(sess, './try.ckpt')
return self.loss, self.accuracy
And ran this code as:
nn = Neural_Network(2, [20,3], [tf.nn.relu, tf.nn.relu], 0.001, optimiser = 'AdamOptimiser')
nn.create_Neural_Net(4)
nn.train_Neural_Net(dataset, labels, 1000)
The error it gives is:
ValueError: No variables to save
So what is wrong in this code? And how can I fix it?