docs: def process_xlsx(content):
      """
      Turn Excel file contents into Tarbell worksheet data
      """
      data = {}
      workbook = xlrd.open_workbook(file_contents=content)
      worksheets = [w for w in workbook.sheet_names() if not w.startswith('_')]
      for worksheet_name in worksheets:
          if worksheet_name.startswith('_'):
              continue
  
          worksheet = workbook.sheet_by_name(worksheet_name)
  
          merged_cells = worksheet.merged_cells
          if len(merged_cells):
              raise MergedCellError(worksheet.name, merged_cells)
  
          worksheet.name = slughifi(worksheet.name)
          headers = make_headers(worksheet)
          worksheet_data = make_worksheet_data(headers, worksheet)
          data[worksheet.name] = worksheet_data
      return data