关于openpyxl 操作Excel的一个小问题，请教大神

from openpyxl.styles import Font, colors, Alignment,Border,Side
Border(left=Side(border_style='medium',
color=colors.BLACK),
right=Side(border_style='medium',
color=colors.BLACK),
top=Side(border_style='medium',
color=colors.BLACK),
bottom=Side(border_style='medium',
color=colors.BLACK),
diagonal=Side(border_style='medium',
color=colors.BLACK),
#diagonalUp = True,
#diagonalDown= True,
！！ diagonal_direction= 0, ！！
outline=Side(border_style='medium',
color=colors.BLACK),
vertical=Side(border_style='medium',
color=colors.BLACK),
horizontal=Side(border_style='medium',
color=colors.BLACK))
其中 Border 下面有一个参数 diagonal_direction= None,
请问这个参数管理的具体是什么？ 要怎么给值啊？