code: def list_worksheets(self):
          
          worksheets = self.get_worksheets()
          return [(x.link[3].href.split('/')[-1], x.title.text)
              for x in worksheets.entry]
docs: List what worksheet keys exist
  
          Returns a list of tuples of the form:
              (WORKSHEET_ID, WORKSHEET_NAME)
          You can then retrieve the specific WORKSHEET_ID in the future by
          constructing a new GSpreadsheet(worksheet=WORKSHEET_ID, ...)