code: def append(self, row_dict):
          
          # TODO validate row_dict.keys() match
          # TODO check self.is_authed
          entry = self.client.InsertRow(row_dict, self.key, self.worksheet)
          self.feed.entry.append(entry)
          return GDataRow(entry, sheet=self, deferred_save=self.deferred_save)
docs: Add a row to the spreadsheet, returns the new row