def neighbors_of(self, qubit: GridQubit):
"""Returns the qubits that the given qubit can interact with."""
possibles = [
GridQubit(qubit.row + 1, qubit.col),
GridQubit(qubit.row - 1, qubit.col),
GridQubit(qubit.row, qubit.col + 1),
GridQubit(qubit.row, qubit.col - 1),
]
return [e for e in possibles if e in self.qubits]
def at(self, row: int, col: int) -> Optional[GridQubit]:
"""Returns the qubit at the given position, if there is one, else None.
"""
q = GridQubit(row, col)
return q if q in self.qubits else None
