def __deepcopy__(self, memo):
addl_msg = '<STR_LIT>'<EOL>_raise_unknown_reference_error(self, addl_msg)<EOL>
Dishonestly implements the __deepcopy__ special method.

        See `ConfigurableReference` above. If this method is called, it means there
        was an attempt to use this unknown configurable reference, so we throw an
        error here.

        Args:
          memo: The memoization dict (unused).

        Raises:
          ValueError: To report that there is no matching configurable.