openpyxl 合并多表多个sheet出错

下面这个程序我像遍历每个工作表的工作簿，但是提示我错误KeyError: "Worksheet ['Worksheet1', 'Sheet1'] does not exist." 但是这两个sheet都存在啊，有人知道怎么回事么？

def merge_xlsx_files(xlsx_files):
wb = openpyxl.load_workbook(xlsx_files[0])
ws = wb.active
ws.title = "merged result"

for  filename in xlsx_files[1:]:
    workbook = openpyxl.load_workbook(filename)
    
    #sheet = workbook.active
    Sname = workbook.sheetnames   #这里有两个 sheet ：'Worksheet1', 'Sheet1'
    for sheet in Sname:
        sheet =wb[Sname]
        for row in sheet.iter_rows(min_row=1):   
            values = [cell.value for cell in row]
            ws.append(values)
return wb

    sheet =wb[Sname]   这一句是什么意思  ？ 应该是wb[sheet] 吧 这里应该是每个单独sheet name吧