message: Add `dtype` property to RaggedTensorSpec
diff: @@ -2264,6 +2264,11 @@ class RaggedTensorSpec(type_spec.BatchableTypeSpec):
  else:
  return super(RaggedTensorSpec, self).is_compatible_with(spec_or_value)
  + @property
  + def dtype(self):
  + """The `tf.dtypes.DType` specified by this type for the RaggedTensor."""
  + return self._dtype
  +
  def _serialize(self):
  return (self._shape, self._dtype, self._ragged_rank, self._row_splits_dtype)
  