def hash_board(self, board: chess.BaseBoard) -> int:
zobrist_hash = 0
for pivot, squares in enumerate(board.occupied_co):
for square in chess.scan_reversed(squares):
piece_index = (typing.cast(chess.PieceType, board.piece_type_at(square)) - 1) * 2 + pivot
zobrist_hash ^= self.array[64 * piece_index + square]
return zobrist_hash
