title: keras.utils.plot_model doesn't show me the graphic
body: <p>I´m learning Keras and TensorFlow, I´m trying to run a sample code that has keras.utils.plot_model instruction and he doesn´t show me the graphic, the other part of code work very well, but at the end, I can´t see the graphic that the program should show me. I have 2 days trying to solve this problem but I could not do it. This is the code:</p>
  
  <pre class="lang-py prettyprint-override"><code>import numpy as np    
  import tensorflow as tf
  from tensorflow import keras
  from tensorflow.keras import layers
  
  inputs = keras.Input(shape=(784,))
  print(inputs.shape) 
  print(inputs.dtype) 
  
  dense = layers.Dense(64, activation="relu")
  x = dense(inputs) 
  x = layers.Dense(64, activation="relu")(x) 
  outputs = layers.Dense(10)(x)
  
  model = keras.Model(inputs=inputs, outputs=outputs, name="mnist_model")
  print(model.summary())
  
  keras.utils.plot_model(model, "my_first_model.png")
  
  </code></pre>
  
  <p>This is the model result, that doesn´t show me the graphic:</p>
  
  <pre><code>(None, 784)
  &lt;dtype: 'float32'&gt;
  2020-06-14 13:24:33.233826: I tensorflow/core/platform/cpu_feature_guard.cc:142] Your CPU supports instructions that this TensorFlow binary was not compiled to use: AVX2
  Model: "mnist_model"
  _________________________________________________________________
  Layer (type)                 Output Shape              Param #
  =================================================================
  input_1 (InputLayer)         [(None, 784)]             0
  _________________________________________________________________
  dense (Dense)                (None, 64)                50240
  _________________________________________________________________
  dense_1 (Dense)              (None, 64)                4160
  _________________________________________________________________
  dense_2 (Dense)              (None, 10)                650
  =================================================================
  Total params: 55,050
  Trainable params: 55,050
  Non-trainable params: 0
  _________________________________________________________________
  None
  </code></pre>
  
  <p>I´m using these versions:</p>
  
  <pre><code>- Pydot 1.4.1
  - Graphviz 2.38
  - TensorFlow 2.0.0
  - Python 3.7.0
  </code></pre>
  
  <p><strong>Why I can´t see the graphic?</strong></p>