def has_disk_at(board, position):
    """
        Check whether a disk is stored at the given position on the given board.
        - The function returns false if no disk can be obtained from the given
          board at the given position.
        ASSUMPTIONS
        - The given board is a proper board and the given position is a
          proper position for that board.
    """
    if board[position] is None:
        return False
    return True