docstr: Get the file representing the given submodule nesting.
  List may be empty for top-level api module.
  
  When the file is accessed the first time, it's header and submodule imports are
  written.
code: def get(self, module_nesting: List[str]):
      """Get the file representing the given submodule nesting.
      List may be empty for top-level api module.
  
      When the file is accessed the first time, it's header and submodule imports are
      written.
      """
      module_path = Path("/".join(module_nesting))
      if module_path not in self._module_to_file:
          file_path = (
              self._nvidia_dali_path
              / self._api
              / module_path
              / "__init__.pyi"
          )
          os.makedirs(os.path.dirname(file_path), exist_ok=True)
          open(file_path, "w").close()  # clear the file
          f = open(file_path, "a")
          self._module_to_file[module_path] = f
          f.write(_HEADER)
          full_module_nesting = [""] + module_nesting
          # Find out all the direct submodules and add the imports
          submodules_dict = self._module_tree
          for submodule in full_module_nesting:
              submodules_dict = submodules_dict[submodule]
          direct_submodules = submodules_dict.keys()
          for direct_submodule in direct_submodules:
              f.write(
                  f"from . import {direct_submodule} as {direct_submodule}\n"
              )
  
          f.write("\n\n")
      return self._module_to_file[module_path]
  
imports: from inspect import Parameter, Signature
  import ast
  import os
  from pathlib import Path
  from contextlib import closing
  from typing import Union, Optional
  from typing import Sequence, List, Any
  from nvidia.dali import backend
  from nvidia.dali import types
  from nvidia.dali.ops import _registry, _names, _docs
  from nvidia.dali import types
  from nvidia.dali import ops, fn
label_desc: Use image node_id 2 for calling the StubFileManager obj's underlying member method code with example usage: obj.get(module_nesting) and returns: self