Reportlab表

Question

我正在尝试使用Reportlab构建一个图例（通过表格）。该表应该有三行和两列，每个i，j元素是一个带有彩色子弹点的ListItem。这是代码：

    ptext = '<font size=10><b><i>Legend:</i></b></font>'
    light = []
    mild = []
    strong = []

    #Create the table
    ptext = '<font size=10>Light Barrier</font>'
    light.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = lightRed, value = 'circle'), bulletType = 'bullet', start = 'circle'))
    ptext = '<font size=10>Light Benefit</font>'
    light.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = lightGreen, value = 'circle'), bulletType = 'bullet', start = 'circle'))
    ptext = '<font size=10>Mild Barrier</font>'
    mild.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = mildRed, value = 'circle'), bulletType = 'bullet', start = 'circle'))
    ptext = '<font size=10>Mild Benefit</font>'
    mild.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = mildGreen, value = 'circle'), bulletType = 'bullet', start = 'circle'))
    ptext = '<font size=10>Strong Barrier</font>'
    strong.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = strongRed, value = 'circle'), bulletType = 'bullet', start = 'circle'))
    ptext = '<font size=10>Strong Benefit</font>'
    strong.append(ListFlowable(ListItem(Paragraph(ptext, styles["Normal"]), 
                               bulletColor = strongGreen, value = 'circle'), bulletType = 'bullet', start = 'circle'))

    #Append them to the table
    data = [light, mild, strong]
    t = Table(data)
    Story.append(t)

我得到的错误说：

“ListItem不可迭代”。

任何帮助表示赞赏。