def _circuit_diagram_info_(self, args: cirq.CircuitDiagramInfoArgs) -> cirq.CircuitDiagramInfo:
        """Returns a string representation to be used in circuit diagrams."""

        def get_symbol(vals):
            return '@' if tuple(vals) == (1,) else f"({','.join(map(str, vals))})"

        return protocols.CircuitDiagramInfo(wire_symbols=[get_symbol(t) for t in self._qubit_sums])
Returns a string representation to be used in circuit diagrams.
cirq-core/cirq/ops/control_values.py