title: TensorFlow :ValueError: None values not supported
body: <pre><code>import tensorflow as tf
  import matplotlib.pyplot as plt
  
  from tensorflow.examples.tutorials.mnist import input_data
  
  mnist=input_data.read_data_sets('MNIST_DATA/',one_hot=True)
  def init_weights(shape):
      init_random_dist=tf.truncated_normal(shape,stddev=0.1)
  
      return tf.Variable(init_random_dist)
  def init_bias(shape):
      init_bias_vals=tf.constant(0.1,shape=shape)
      return tf.Variable(init_bias_vals)
  def conv2d(x,W):
  
      return tf.nn.conv2d(x,W,strides=[1,1,1,1],padding='SAME')
  def max_pool_2by2(x):
      tf.nn.max_pool(x,ksize=[1,2,2,1],strides=[1,2,2,1],padding='SAME')
  def conv(input_x,shape):
      W=init_weights(shape)
      b=init_bias([shape[3]])
      return tf.nn.relu(conv2d(input_x,W)+b )
  def normal(input_layer,size):
      input_size=int(input_layer.get_shape()[1])
      W=init_weights([input_size,size])
      b=init_bias([size])
      return tf.matmul(input_layer,W)+b
  x=tf.placeholder(tf.float32,shape=[None,784])
  y_true=tf.placeholder(tf.float32,shape=[None,10])
  x_image=tf.reshape(x,[-1,28,28,1])
  
   conv1=conv(x_image,shape=[5,5,1,32])
   conv1_pooling=max_pool_2by2(conv1)
  # # conv2=conv(conv1_pooling,shape=[5,5,32,64])
   conv2=conv(conv1_pooling,shape=[5,5,32,64])
   conv2_pooling=max_pool_2by2(conv2)
   conv2_flat=tf.reshape(conv2_pooling,[-1,7*7*64])
   full_layer=tf.nn.relu(normal(conv2_flat,1024))
  </code></pre>
  
  <p>but when i tried to run this code i ran in to a strange error </p>
  
  <pre><code>ValueError: None values not supported.
  
  During handling of the above exception, another exception occurred:
  </code></pre>
  
  <p>all those code was learn't from a tutorial but when i tried to run the jupyter notebook of that tutorial the code executed well and there was no issue or error after execution 
  i dont know the reason why my code is popping up with an error </p>
  
  <p>any kind of help is appreciated 
  EDIT1: i didnt run this code in tensorflow session 
  following the tutorial the tutor told  to  run this code in order to check any kind of issues </p>