def METHOD_NAME(node, classDef):
    """Add reference on classDef to node"""
    ref = addnodes.pending_xref(
        reftarget=classDef,
        reftype="class",
        refdomain="py",  # py:class="None" py:module="altair" refdoc="user_guide/marks"
        refexplicit=False,
        # refdoc="",
        refwarn=False,
    )
    ref["py:class"] = "None"
    ref["py:module"] = "altair"
    ref += nodes.literal(text=classDef, classes=["xref", "py", "py-class"])
    node += ref
    return node