docs: def is_simple(fun):
      """A heuristic to find out if a function is simple enough."""
      seen_load_fast_0 = False
      seen_load_response = False
      seen_call_fun = False
  
      for instruction in dis.get_instructions(fun):
          if instruction.opname == 'LOAD_FAST' and instruction.arg == 0:
              seen_load_fast_0 = True
              continue
  
          if instruction.opname == 'LOAD_ATTR' \
             and instruction.argval == 'Response':
              seen_load_response = True
              continue
  
          if instruction.opname.startswith('CALL_FUNCTION'):
              if seen_call_fun:
                  return False
  
              seen_call_fun = True
              continue
  
      return seen_call_fun and seen_load_fast_0 and seen_load_response