message: Fixes typo (missing space) in padded_batch error
  The error message used to read "... if any component of its inputhas an unknown rank"
diff: @@ -1478,8 +1478,8 @@ class DatasetV2(tracking_base.Trackable, composite_tensor.CompositeTensor):
  # bool(tf.TensorShape(None)) is False
  if not all(nest.flatten(padded_shapes)):
  raise ValueError("You must set the `padded_shapes` argument to "
  - "`Dataset.padded_batch` if any component of its input"
  - "has an unknown rank")
  + "`Dataset.padded_batch` if any component of its "
  + "input has an unknown rank")
  return PaddedBatchDataset(self, batch_size, padded_shapes, padding_values,
  drop_remainder)
  