title: ValueError: Unknown layer: KerasLayer
body: <p>I have the following code: </p>
  
  <pre><code>from keras.models import model_from_json
  
  with open('modelS.json', 'r') as f: 
    json = f.read() 
  loaded_model = model_from_json(json)
  </code></pre>
  
  <p>Here is the json file used in the above code: </p>
  
  <p><code>{"class_name": "Sequential", "config": {"name": "sequential", "layers": [{"class_name": "KerasLayer", "config": {"name": "keras_layer", "trainable": true, "batch_input_shape": [null], "dtype": "string", "handle": "https://tfhub.dev/google/tf2-preview/nnlm-en-dim128/1"}}, {"class_name": "Dense", "config": {"name": "dense", "trainable": true, "dtype": "float32", "units": 16, "activation": "relu", "use_bias": true, "kernel_initializer": {"class_name": "GlorotUniform", "config": {"seed": null}}, "bias_initializer": {"class_name": "Zeros", "config": {}}, "kernel_regularizer": null, "bias_regularizer": null, "activity_regularizer": null, "kernel_constraint": null, "bias_constraint": null}}, {"class_name": "Dense", "config": {"name": "dense_1", "trainable": true, "dtype": "float32", "units": 16, "activation": "relu", "use_bias": true, "kernel_initializer": {"class_name": "GlorotUniform", "config": {"seed": null}}, "bias_initializer": {"class_name": "Zeros", "config": {}}, "kernel_regularizer": null, "bias_regularizer": null, "activity_regularizer": null, "kernel_constraint": null, "bias_constraint": null}}, {"class_name": "Dense", "config": {"name": "dense_2", "trainable": true, "dtype": "float32", "units": 1, "activation": "sigmoid", "use_bias": true, "kernel_initializer": {"class_name": "GlorotUniform", "config": {"seed": null}}, "bias_initializer": {"class_name": "Zeros", "config": {}}, "kernel_regularizer": null, "bias_regularizer": null, "activity_regularizer": null, "kernel_constraint": null, "bias_constraint": null}}], "build_input_shape": [null]}, "keras_version": "2.3.0-tf", "backend": "tensorflow"}</code></p>
  
  <p>But I get the following error from the last line: </p>
  
  <p><code>ValueError: Unknown layer: KerasLayer</code>. </p>
  
  <p>What could be the reason for this?</p>