def remove_qubits(self: Self, qubits: Sequence[cirq.Qid]) -> Self:
        """Remove `qubits` from the state space.

        The qubits to be removed should be untangled from rest of the system and in the |0> state.

        Args:
            qubits: Sequence of qubits to be removed.

        Returns:
            NotImplemented: If the subclass does not implement this method.
            Self: A `cirq.SimulationState` with qubits removed or `self` if there are no qubits to
                remove.
        """
        if not qubits:
            return self
        return NotImplemented
Remove `qubits` from the state space.

        The qubits to be removed should be untangled from rest of the system and in the |0> state.

        Args:
            qubits: Sequence of qubits to be removed.

        Returns:
            NotImplemented: If the subclass does not implement this method.
            Self: A `cirq.SimulationState` with qubits removed or `self` if there are no qubits to
                remove.
        
cirq-core/cirq/sim/simulation_state.py