class_docstr: Writes a single pyi file
class_docstr_tok: ["Writes","a","single","pyi","file"]
code: def __init__(
      self, fd: d.FileDescriptorProto, descriptors: Descriptors
  ) -> None:
      self.fd = fd
      self.descriptors = descriptors
      self.lines: List[str] = []
      self.indent = ""
  
      # dictionary of x->y for `from {x} import {y}`
      self.imports: Dict[str, Set[str]] = defaultdict(set)
      self.locals: Set[str] = set()
  
file_path: onnx/tools/protoc-gen-mypy.py
imports: import sys
  from collections import defaultdict
  from contextlib import contextmanager
  from typing import Any, Callable, Dict, Generator, List, Optional, Set, cast
label_desc: Use image node_id 1 to create a new PkgWriter object  with example: obj = PkgWriter(fd, descriptors)