docs: def extend_rows(self, list_or_dict):
          """ Add multiple rows at once
  
          :param list_or_dict: a 2 dimensional structure for adding multiple rows at once
          :return:
          """
          if isinstance(list_or_dict, list):
              for r in list_or_dict:
                  self.add_row(r)
          else:
              for k,r in list_or_dict.iteritems():
                  self.add_row(r, k)