code: def dump_subtask_graph(self):
      from .graph_visualizer import GraphVisualizer
  
      try:  # pragma: no cover
          import graphviz
      except ImportError:
          graphviz = None
  
      dot = GraphVisualizer.to_dot(self._subtask_graphs)
      directory = os.environ.get("MARS_DUMP_SUBTASK_GRAPH_DIR")
      if directory is None:
          directory = tempfile.gettempdir()
      os.makedirs(directory, exist_ok=True)
      file_name = f"mars-{self.task_id}"
      logger.info(
          "Subtask graph of task %s is stored in %s",
          self._task.task_id,
          os.path.join(directory, file_name),
      )
      if graphviz is not None:  # pragma: no cover
          try:
              g = graphviz.Source(dot)
              g.view(file_name, directory=directory)
              return
          except graphviz.ExecutableNotFound:  # pragma: no cover
              logger.info(
                  "dot executable is not found, dump dot file instead."
              )
  
      with open(os.path.join(directory, file_name), "w") as f:
          f.write(dot)
  
imports: import asyncio
  import logging
  import os
  import tempfile
  import time
  from typing import Dict, Iterator, Optional, List, Set
  from ....core import ChunkGraph, TileableGraph, Chunk, TileContext
  from ....core.operand import Fetch
  from ....metrics import Metrics
  from ....optimization.logical import OptimizationRecords
  from ....oscar.profiling import ProfilingData, MARS_ENABLE_PROFILING
  from ....typing import TileableType, ChunkType
  from ....utils import Timer
  from ...subtask import SubtaskResult, Subtask
  from ..core import Task, TaskResult, TaskStatus, new_task_id, MapReduceInfo
  from ..execution.api import TaskExecutor, ExecutionChunkResult
  from .preprocessor import TaskPreprocessor
label_desc: Use image node_id 16 for calling the TaskProcessor obj's underlying member method code with example usage: obj.dump_subtask_graph() without return types