message: fix(python): ValueError len(dataframe.columns) + 1
diff: @@ -250,7 +250,7 @@ class _PandasFeedFn(object):
  num_epochs=None):
  if len(placeholders) != len(dataframe.columns) + 1:
  raise ValueError("Expected {} placeholders; got {}.".format(
  - len(dataframe.columns), len(placeholders)))
  + len(dataframe.columns) + 1, len(placeholders)))
  self._index_placeholder = placeholders[0]
  self._col_placeholders = placeholders[1:]
  self._dataframe = dataframe
  