def METHOD_NAME(self):
    """Returns a copy of the sub-tree.  This should be overridden in
    sub-classes with more data.
    .. note:: ``self.renderer`` is **not** copied.
    """
    from METHOD_NAME import METHOD_NAME
    cp = self.__class__(
        id=self.id, rid=self.rid, xid=self.xid, xml_node=METHOD_NAME(self.xml_node)
    )
    for sub in self.sub:
        if isinstance(sub, StringElem):
            cp.sub.append(sub.METHOD_NAME())
        else:
            cp.sub.append(sub.__class__(sub))
    return cp