def num_qubits(self) -> Optional[int]:
        """Returns number of qubits in the domain if known, None if unknown."""
        if not self:
            return None
        any_gate = next(iter(self))
        return any_gate.num_qubits()
def num_qubits ( self ) -> Optional [ int ] : if not self : return None any_gate = next ( iter ( self ) ) return any_gate . num_qubits ( )
Returns number of qubits in the domain if known, None if unknown.