def _resolved_value_(self) -> Any:
        """Returns a resolved value during parameter resolution.

        Use this to mark a custom type as "resolved", instead of requiring
        further parsing like we do with Sympy symbols.
        """
Returns a resolved value during parameter resolution.

        Use this to mark a custom type as "resolved", instead of requiring
        further parsing like we do with Sympy symbols.
        
cirq-core/cirq/protocols/resolve_parameters.py