title: 'str' object has no attribute 'base_dtype' error TensorFlow model
body: <p>I am implementing a Wasserstein DCGAN in TensorFlow.
  This is my generator model :</p>
  
  <pre><code>w1 = tf.get_variable('w1', shape=[random_dim, 1024], dtype=tf.float32,
                               initializer=tf.contrib.layers.xavier_initializer())
  b1 =  b1 = tf.get_variable('b1', shape=[1024], dtype=tf.float32,
                       initializer=tf.constant_initializer(1.0))
  flat_conv1 = tf.add(tf.matmul(input , w1) , b1 , name = 'flat_conv1')
  act1 = tf.nn.tanh(flat_conv1, name='act1')
  
  dense1 = tf.layers.dense(bias_initializer=tf.ones_initializer(),inputs=act1, units=128*7*7, activation=tf.nn.tanh , kernel_initializer = tf.contrib.layers.xavier_initializer())
  bn1 = tf.contrib.layers.batch_norm(dense1, is_training=is_train, epsilon=1e-5, decay = 0.9,  updates_collections=None, scope='bn1')
  act2 = tf.nn.tanh(bn1, name='act1')
  
  conv1 = tf.reshape(act2, shape=[-1,7,7,128], name='conv1')
  up1 = tf.keras.layers.UpSampling2D(size = (2,2))
  
  conv2 = tf.layers.conv2d(bias_initializer=tf.ones_initializer(),inputs=up1,filters=64,kernel_size=[5, 5],padding="same",activation=tf.nn.tanh , kernel_initializer = tf.contrib.layers.xavier_initializer())
  up2 = tf.keras.layers.UpSampling2D(size = (2,2))
  conv3 = tf.layers.conv2d(bias_initializer=tf.ones_initializer(),inputs=up2,filters =1,kernel_size=[5, 5],padding= "same",activation=tf.nn.tanh , kernel_initializer = tf.contrib.layers.xavier_initializer())
  </code></pre>
  
  <p>The error is in the conv2 layer and it says - ''str' object has no attribute 'base_dtype'
  I am a newbie to TensorFlow and cannot figure out why is it so.
  COMPLETE SOURCE CODE : <a href="https://github.com/tanmay-bhatnagar/W-DCGAN" rel="nofollow noreferrer">https://github.com/tanmay-bhatnagar/W-DCGAN</a>
  Obtained <code>train</code> function from here :<a href="https://github.com/llSourcell/Pokemon_GAN/blob/master/pokeGAN.py" rel="nofollow noreferrer">https://github.com/llSourcell/Pokemon_GAN/blob/master/pokeGAN.py</a></p>
  
  <p>Please ask for any further details that are required.</p>