title: no add_to_collection was found when using tensorflowjs_converter
body: <p>I am trying to convert a savedModel into TensorFlow.js web format.</p>
  
  <p>I installed tensorflowjs via <code>sudo pip3 install tensorflowjs</code></p>
  
  <p>When running <code>tensorflowjs_converter--input_path=full_path_to/saved_model/saved_model.pb --outputpath=full_path_to/js</code></p>
  
  <p>I get an error saying  <em>ImportError: cannot import name 'add_to_collection'</em></p>
  
  <p>Even if I run <code>tensorflowjs_converter --help</code>, I get the exact same error.</p>
  
  <p>Here is the full error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflow_hub/tf_v1.py", line 29, in &lt;module&gt;
      from tensorflow.compat.v1 import *  # pylint: disable=wildcard-import
  ModuleNotFoundError: No module named 'tensorflow.compat.v1'
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/home/ubuntu/.local/bin/tensorflowjs_converter", line 7, in &lt;module&gt;
      from tensorflowjs.converters.converter import main
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflowjs/__init__.py", line 21, in &lt;module&gt;
      from tensorflowjs import converters
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflowjs/converters/__init__.py", line 24, in &lt;module&gt;
      from tensorflowjs.converters.tf_saved_model_conversion_v2 import convert_tf_saved_model
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflowjs/converters/tf_saved_model_conversion_v2.py", line 37, in &lt;module&gt;
      import tensorflow_hub as hub
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflow_hub/__init__.py", line 30, in &lt;module&gt;
      from tensorflow_hub.estimator import LatestModuleExporter
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflow_hub/estimator.py", line 25, in &lt;module&gt;
      from tensorflow_hub import tf_utils
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflow_hub/tf_utils.py", line 28, in &lt;module&gt;
      from tensorflow_hub import tf_v1
    File "/home/ubuntu/.local/lib/python3.6/site-packages/tensorflow_hub/tf_v1.py", line 32, in &lt;module&gt;
      from tensorflow import add_to_collection
  ImportError: cannot import name 'add_to_collection'
  </code></pre>