code: def __init__(
      self, service=None, session=None, backend=None, n_parallel=None
  ):
      super().__init__()
  
      if session is None:
          if service is not None:
              self.session = new_session(
                  service, backend=backend, default=False
              )
          else:
              self.session = get_default_session()
      else:
          self.session = session
  
      self.n_parallel = n_parallel or 1
      self.executor = None
  
file_path: mars/mars/learn/contrib/joblib/backend.py
imports: import concurrent.futures
  from ....None import remote
  from ....session import get_default_session, new_session
label_desc: Use image node_id 1 to create a new MarsDistributedBackend object from inherited base classes: AutoBatchingMixin, ParallelBackendBase with example: obj = MarsDistributedBackend(service, session, backend, n_parallel)