def add(self, revision, operators):
ir = IndexedRevision(<EOL>revision=revision, operators=[operator.name for operator in operators]<EOL>)<EOL>self._revisions[revision.key] = ir<EOL>return ir<EOL>
Add a revision to the index.

:param revision: The revision.
:type  revision: :class:`Revision` or :class:`LazyRevision`