code: def monitor_tasks(self):
      return self._monitor_tasks
  
imports: import asyncio
  import time
  import pandas
  import pytest
  import numpy
  from collections import Counter
  from ......None import dataframe
  from ......None import tensor
  from ......config import Config
  from ......core import TileContext
  from ......core.context import get_context
  from ......core.graph import TileableGraph, TileableGraphBuilder, ChunkGraphBuilder
  from ......core.operand import ShuffleFetchType
  from ......lib.aio.isolation import new_isolation, stop_isolation
  from ......resource import Resource
  from ......serialization import serialize
  from ......tests.core import require_ray, mock
  from ......utils import lazy_import, get_chunk_params
  from .....context import ThreadedServiceContext
  from .....subtask import Subtask
  from ....analyzer import GraphAnalyzer
  from ....core import new_task_id, Task
  from ..config import RayExecutionConfig
  from ..context import RayExecutionContext, RayExecutionWorkerContext, RayRemoteObjectManager, _RayRemoteObjectContext
  from ..executor import execute_subtask, OrderedSet, RayTaskExecutor, RayTaskState, _RayChunkMeta, _RaySubtaskRuntime, _RaySlowSubtaskChecker
  from ..fetcher import RayFetcher
  from ..shuffle import ShuffleManager
label_desc: Use image node_id 3 for calling the MockRayTaskExecutor obj's underlying member method code with example usage: obj.monitor_tasks() and returns: self