code: def __str__(self):
      return (
          "No event loop integration for {!r}. "
          "Supported event loops are: {}"
      ).format(self.name, ", ".join(backends + sorted(registered)))
  
file_path: catboost/contrib/python/ipython/py3/IPython/terminal/pt_inputhooks/__init__.py
imports: import importlib
  import os
  from typing import Tuple, Callable
label_desc: Use image node_id 2 for calling the UnknownBackend obj's underlying member method code with example usage: obj.__str__() and returns: str