'Return newly added |_Relationship| instance of *reltype* between this
part and *target* with key *rId*. Target mode is set to
``RTM.EXTERNAL`` if *is_external* is |True|. Intended for use during
load from a serialized package, where the rId is well-known. Other
methods exist for adding a new relationship to a part when
manipulating a part.'

def load_rel(self, reltype, target, rId, is_external=False):

    return self.rels.add_relationship(reltype, target, rId, is_external)
