docs: def get_instance_id(self, instance):
          " Returns instance pk even if multiple instances were passed to RichTextField. "
          if type(instance) in [list, tuple]:
              core_signals.request_finished.connect(receiver=RichTextField.reset_instance_counter_listener)
              if RichTextField.__inst_counter >= len(instance):
                  return None
              else:
                  obj_id = self.instance[ RichTextField.__inst_counter ].pk
              RichTextField.__inst_counter += 1
          else:
              obj_id = instance.pk
          return obj_id