def _parity_interaction(q0: ops.Qid,
                        q1: ops.Qid,
                        rads: float,
                        atol: float,
                        gate: Optional[ops.Gate] = None):
    """Yields an XX interaction framed by the given operation."""

    if abs(rads) < atol:
        return

    if gate is not None:
        g = cast(ops.Gate, gate)
        yield g.on(q0), g.on(q1)

    yield MS(-1 * rads).on(q0, q1)

    if gate is not None:
        g = protocols.inverse(gate)
        yield g.on(q0), g.on(q1)
Yields an XX interaction framed by the given operation.