code: def _cleanup_unregistered_flag_from_module_dicts(self, flag_obj):
      
      if self._flag_is_registered(flag_obj):
        return
      for flags_by_module_dict in (self.flags_by_module_dict(),
                                   self.flags_by_module_id_dict(),
                                   self.key_flags_by_module_dict()):
        for flags_in_module in six.itervalues(flags_by_module_dict):
          # While (as opposed to if) takes care of multiple occurrences of a
          # flag in the list for the same module.
          while flag_obj in flags_in_module:
            flags_in_module.remove(flag_obj)
docs: Cleans up unregistered flags from all module -> [flags] dictionaries.
  
      If flag_obj is registered under either its long name or short name, it
      won't be removed from the dictionaries.
  
      Args:
        flag_obj: Flag, the Flag instance to clean up for.