title: Featuretools TypeError: unhashable type: 'Int64Index'
body: <p>I am trying to create an entity set from 3 dataframes and while doing so I am getting the error: TypeError: unhashable type: 'Int64Index'</p>
  
  <p>I have searched the Internet for similar issues but could not find any issues related to datetime types. Please note that none of the columns of df_raw_view_logs are unique and hence none of the columns can be used as index value and hence the dataframe.index is being used.</p>
  
  <p>I am sharing the dtypes for the dataframe for which it is throwing error when I make a column from it as a time index.</p>
  
  <pre><code>df_raw_view_logs.dtypes
  
  server_time    datetime64[ns]
  device_type              int8
  session_id              int64
  user_id                 int64
  item_id                 int64
  dtype: object
  
  es = ft.EntitySet()
  es = es.entity_from_dataframe(entity_id="train", 
                            dataframe=df_es_train,
                            index=df_es_train.index,
                            time_index="impression_time",
                            )
  
  es = es.entity_from_dataframe(entity_id="viewlogs", 
                            dataframe=df_es_view_logs,
                            index=df_es_view_logs.index,
                            time_index="server_time",
                            )
  
  es = es.entity_from_dataframe(entity_id="itemdata", 
                            dataframe=df_es_item_data,
                            index=df_es_item_data.index,
                            )
  
  new_relationship = ft.Relationship(es["train"]["user_id"],
                                 es["viewlogs"]["user_id"])
  es = es.add_relationship(new_relationship)
  new_relationship_1 = ft.Relationship(es["viewlogs"]["item_id"],
                                 es["itemdata"]["item_id"])
  es = es.add_relationship(new_relationship_1)
  
      ---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-32-81425e9b87c5&gt; in &lt;module&gt;
        9                               dataframe=df_es_view_logs,
       10                               index=df_es_view_logs.index,
  ---&gt; 11                               time_index="server_time",
       12                               )
       13 
  
  D:\Anaconda3\envs\fastai\lib\site-packages\featuretools\entityset\entityset.py in entity_from_dataframe(self, entity_id, dataframe, index, variable_types, make_index, time_index, secondary_time_index, already_sorted)
      495             secondary_time_index=secondary_time_index,
      496             already_sorted=already_sorted,
  --&gt; 497             make_index=make_index)
      498         self.entity_dict[entity.id] = entity
      499         self.reset_data_description()
  
  D:\Anaconda3\envs\fastai\lib\site-packages\featuretools\entityset\entity.py in __init__(self, id, df, entityset, variable_types, index, time_index, secondary_time_index, last_time_index, already_sorted, make_index, verbose)
       67         """
       68         _validate_entity_params(id, df, time_index)
  ---&gt; 69         created_index, index, df = _create_index(index, make_index, df)
       70 
       71         self.id = id
  
  D:\Anaconda3\envs\fastai\lib\site-packages\featuretools\entityset\entity.py in _create_index(index, make_index, df)
      547         # Case 3: user wanted to make index but column already exists
      548         raise RuntimeError("Cannot make index: index variable already present")
  --&gt; 549     elif index not in df.columns:
      550         if not make_index:
      551             # Case 4: user names index, it is not in df. does not specify
  
  D:\Anaconda3\envs\fastai\lib\site-packages\pandas\core\indexes\base.py in __contains__(self, key)
     3917     @Appender(_index_shared_docs['contains'] % _index_doc_kwargs)
     3918     def __contains__(self, key):
  -&gt; 3919         hash(key)
     3920         try:
     3921             return key in self._engine
  
  D:\Anaconda3\envs\fastai\lib\site-packages\pandas\core\indexes\base.py in __hash__(self)
     3932 
     3933     def __hash__(self):
  -&gt; 3934         raise TypeError("unhashable type: %r" % type(self).__name__)
     3935 
     3936     def __setitem__(self, key, value):
  
  TypeError: unhashable type: 'Int64Index'
  </code></pre>