t revision was emitted by this method call.
        * A delta for that revision was emitted by this method call.
        * ``assumehaveparentrevisions`` is True and the base revision is a
          parent of the node.

        ``nodesorder`` can be used to control the order that revisions are
        emitted. By default, revisions can be reordered as long as they are
        in DAG topological order (see above). If the value is ``nodes``,
        the iteration order from ``nodes`` should be used. If the value is
        ``storage``, then the native order from the backing storage layer
        is used. (Not all storage layers will have strong ordering and behavior
        of this mode is storage-dependent.) ``nodes`` ordering can force
        revisions to be emitted before their ancestors, so consumers should
        use it with care.

        The ``linknode`` attribute on the returned ``irevisiondelta`` may not
        be set and it is the caller's responsibility to resolve it, if needed.

        If ``deltamode`` is CG_DELTAMODE_PREV and revision data is requested,
        all revision data should be emitted as deltas against the revision
        emitted just prior. The initial revision should be a delta against its
        1st parent.
        Nr