message: Small code readability improvement.
diff: @@ -1889,12 +1889,12 @@ class _LazyBuilder(object):
  self._feature_tensors[key] = feature_tensor
  return feature_tensor
  - if not isinstance(key, (str, _FeatureColumn)):
  - raise TypeError('"key" must be either a "str" or "_FeatureColumn". '
  - 'Provided: {}'.format(key))
  + if isinstance(key, str):
  + raise ValueError('Feature {} is not in features dictionary.'.format(key))
  if not isinstance(key, _FeatureColumn):
  - raise ValueError('Feature {} is not in features dictionary.'.format(key))
  + raise TypeError('"key" must be either a "str" or "_FeatureColumn". '
  + 'Provided: {}'.format(key))
  column = key
  logging.debug('Transforming feature_column %s.', column)
  