code: def generate_stub_file(self, output_dir) -> None:
      file_str = self._output_stubs()
      if file_str is None or len(file_str) == 0:
          raise Exception("file_str is empty")
  
      output_file = f"{output_dir}/{self._name}.py"
      with open(output_file, "w") as f:
          f.write(file_str)
          f.close()
          if self._format:
              subprocess.Popen(
                  ["autopep8", "-a", "-r", "-i", output_file],
                  stdout=subprocess.PIPE,
              ).communicate()
              subprocess.Popen(
                  ["isort", output_file], stdout=subprocess.PIPE
              ).communicate()
  
imports: import argparse
  import subprocess
  from abc import ABC, abstractmethod
  from typing import Dict, List, Optional
label_desc: Use image node_id 8 for calling the ExternLibrary obj's underlying member method code with example usage: obj.generate_stub_file(output_dir) without return types