title: issue to make TTS model from .pb file to TFlight AttributeError: 'AutoTrackable' object has no attribute 'inputs'
body: <p>Am trying to make TTS model for arabic with tacotron and I have checkpoint successfully generated with training and I stop the train on this point .</p>
  <p>I save the file to .pb file and when I try to convert it to tflite this error appear any help ?</p>
  <p><strong>Code to convert checkpoint to pb</strong></p>
  <pre><code>import os
  import tensorflow as tf
  
  trained_checkpoint_prefix = '/home/kayandeveloper/tacotron/logs-tacotron/model.ckpt-4200'
  export_dir = os.path.join('/home/kayandeveloper/tacotron/', '0')
  
  graph = tf.Graph()
  with tf.compat.v1.Session(graph=graph) as sess:
      # Restore from checkpoint
      loader = tf.compat.v1.train.import_meta_graph(trained_checkpoint_prefix + '.meta')
      loader.restore(sess, trained_checkpoint_prefix)
  
      # Export checkpoint to SavedModel
      builder = tf.compat.v1.saved_model.builder.SavedModelBuilder(export_dir)
      builder.add_meta_graph_and_variables(sess,
                                           [tf.saved_model.TRAINING, tf.saved_model.SERVING],
                                           strip_default_attrs=True)
      builder.save()    
  </code></pre>
  <p><strong>Code that I use to convert pb file to tflight</strong></p>
  <pre><code>import tensorflow as tf
  
  # Convert the model
  converter = tf.lite.TFLiteConverter.from_keras_model_file('/home/kayandeveloper/tacotron/0') # path to the SavedModel directory
  tflite_model = converter.convert()
  
  # Save the model.
  with open('/home/kayandeveloper/tacotron/araby.tflite', 'wb') as f:
    f.write(tflite_model)
  </code></pre>
  <p><em><strong>Error log :</strong></em></p>
  <pre><code>2022-02-20 10:30:43.207065: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:983] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
  2022-02-20 10:30:43.207567: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1639] Found device 0 with properties: 
  name: Tesla T4 major: 7 minor: 5 memoryClockRate(GHz): 1.59
  pciBusID: 0000:00:04.0
  2022-02-20 10:30:43.207651: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcudart.so.11.0
  2022-02-20 10:30:43.207699: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcublas.so.11
  2022-02-20 10:30:43.207722: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcufft.so.10
  2022-02-20 10:30:43.207742: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcurand.so.10
  2022-02-20 10:30:43.207761: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcusolver.so.10
  2022-02-20 10:30:43.207789: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcusparse.so.11
  2022-02-20 10:30:43.207810: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library libcudnn.so.8
  2022-02-20 10:30:43.207912: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:983] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
  2022-02-20 10:30:43.208728: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:983] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
  2022-02-20 10:30:43.209109: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1767] Adding visible gpu devices: 0
  2022-02-20 10:30:43.209168: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1180] Device interconnect StreamExecutor with strength 1 edge matrix:
  2022-02-20 10:30:43.209181: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1186]      0 
  2022-02-20 10:30:43.209190: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1199] 0:   N 
  2022-02-20 10:30:43.209328: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:983] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
  2022-02-20 10:30:43.209784: I tensorflow/stream_executor/cuda/cuda_gpu_executor.cc:983] successful NUMA node read from SysFS had negative value (-1), but there must be at least one NUMA node, so returning NUMA node zero
  2022-02-20 10:30:43.210145: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1325] Created TensorFlow device (/job:localhost/replica:0/task:0/device:GPU:0 with 14160 MB memory) -&gt; physical GPU (device: 0, name: Tesla T4, pci bus id: 0000:00:04.0, compute capability: 7.5)
  ---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  /tmp/ipykernel_27138/2295115983.py in &lt;module&gt;
        2 
        3 # Convert the model
  ----&gt; 4 converter = tf.lite.TFLiteConverter.from_keras_model_file('/home/kayandeveloper/tacotron/0') # path to the SavedModel directory
        5 tflite_model = converter.convert()
        6 
  
  /opt/conda/lib/python3.7/site-packages/tensorflow_core/lite/python/lite.py in from_keras_model_file(cls, model_file, input_arrays, input_shapes, output_arrays, custom_objects)
      825       input_tensors = _get_tensors_from_tensor_names(sess.graph, input_arrays)
      826     else:
  --&gt; 827       input_tensors = keras_model.inputs
      828 
      829     if output_arrays:
  
  AttributeError: 'AutoTrackable' object has no attribute 'inputs'
  
  
  </code></pre>