@classmethod
def to_yaml(cls, representer, node):
    """A YAML representation of this Transformation, including all its
        arguments (which must again be YAML-representable). In essence, this
        returns a YAML mapping that has the ``!dag_trf`` YAML tag prefixed,
        such that *reading* it in will lead to the ``from_yaml`` method being
        invoked.

        .. note::

            The YAML representation does *not* include the ``file_cache``
            parameters.

        .. warning::

            The YAML representation is used in computing the hashstr that
            identifies this transformation.
            Changing the argument order here or adding further keys to the
            dict will lead to hash changes and thus to cache misses.

        """
    d = dict(operation=node._operation, args=node._args, kwargs=dict(node.
        _kwargs))
    if node._salt is not None:
        d['salt'] = node._salt
    return representer.represent_mapping(cls.yaml_tag, d)
