title: Tensorflow: ValueError: Expected non-integer, got <dtype: 'int32'>
body: <p>I'm just starting with Tensorflow and when I call <code>m.fit(input_fn=lambda: self.input_fn(train_data), steps=train_steps)</code>, then I receive the following error.</p>
  
  <pre><code>File "/Library/Python/2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column_ops.py", line 161, in _input_from_feature_columns
      transformed_tensor = transformer.transform(column)
  File "/Library/Python/2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column_ops.py", line 882, in transform
      feature_column.insert_transformed_feature(self._columns_to_tensors)
  File "/Library/Python/2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column.py", line 991, in insert_transformed_feature
      self.sparse_id_column.insert_transformed_feature(columns_to_tensors)
  File "/Library/Python/2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column.py", line 572, in insert_transformed_feature
      name="lookup")
  File "/Library/Python/2.7/site-packages/tensorflow/contrib/lookup/lookup_ops.py", line 1018, in index_table_from_tensor
      "integer" if dtype.is_integer else "non-integer", keys.dtype))
  ValueError: Expected non-integer, got &lt;dtype: 'int32'&gt;.
  </code></pre>
  
  <p>In the feature columns that I pass to <code>fit()</code>, there are only <code>int32</code>and <code>int64</code>, but that should not be the problem, should it?</p>