def successors(self, ml: MazeLocation) -> List[MazeLocation]: # 记录运动的路线 locations: List[MazeLocation] = [] if ml.row + 1 < self._rows and self._grid[ml.row + 1][ml.column] != Cell.BLOCKED: locations.append(MazeLocation(ml.row + 1, ml.column)) if ml.row - 1 >= 0 and self._grid[ml.row - 1][ml.column] != Cell.BLOCKED: locations.append(MazeLocation(ml.row - 1, ml.column)) if ml.column + 1 < self._columns and self._grid[ml.row][ml.column + 1] != Cell.BLOCKED: locations.append(MazeLocation(ml.row, ml.column + 1)) if ml.column - 1 >= 0 and self._grid[ml.row][ml.column - 1] != Cell.BLOCKED: locations.append(MazeLocation(ml.row, ml.column - 1)) return locations每行什么意思帮我加上注释

这段代码是一个迷宫问题中的寻找后继节点的函数，下面是每行的注释：

def successors(self, ml: MazeLocation) -> List[MazeLocation]:  # 获取当前节点的后继节点
    locations: List[MazeLocation] = []  # 新建一个list用于存储后继节点
    if ml.row + 1 < self._rows and self._grid[ml.row + 1][ml.column] != Cell.BLOCKED:  # 如果下一行不越界且下一行的方格不是障碍，则添加到后继节点列表中
        locations.append(MazeLocation(ml.row + 1, ml.column))
    if ml.row - 1 >= 0 and self._grid[ml.row - 1][ml.column] != Cell.BLOCKED:  # 如果上一行不越界且上一行的方格不是障碍，则添加到后继节点列表中
        locations.append(MazeLocation(ml.row - 1, ml.column))
    if ml.column + 1 < self._columns and self._grid[ml.row][ml.column + 1] != Cell.BLOCKED:  # 如果下一列不越界且下一列的方格不是障碍，则添加到后继节点列表中
        locations.append(MazeLocation(ml.row, ml.column + 1))
    if ml.column - 1 >= 0 and self._grid[ml.row][ml.column - 1] != Cell.BLOCKED:  # 如果上一列不越界且上一列的方格不是障碍，则添加到后继节点列表中
        locations.append(MazeLocation(ml.row, ml.column - 1))
    return locations  # 返回后继节点列表