code: def py4j_backend(op):
      from hail.backend.py4j_backend import Py4JBackend
  
      b = Env.backend()
      if isinstance(b, Py4JBackend):
          return b
      else:
          raise NotImplementedError(
              f"{b.__class__.__name__} doesn't support {op}, only Py4JBackend"
          )
  
imports: from typing import Optional, Union
  import sys
  import re
  from hailtop.config import ConfigVariable, configuration_of
label_desc: Use image node_id 6 for calling the Env obj's underlying member method code with example usage: obj.py4j_backend(op) and returns: b