class_docstr: Writes a single pyi file
class_docstr_tok: ["Writes","a","single","pyi","file"]
code: def _import_casttype(self, casttype: str) -> str:
      split = casttype.split(".")
      assert (
          len(split) == 2
      ), "mypy_protobuf.[casttype,keytype,valuetype] is expected to be of format path/to/file.TypeInFile"
      pkg = split[0].replace("/", ".")
      return self._import(pkg, split[1])
  
imports: from __future__ import annotations
  import sys
  from collections import defaultdict
  from contextlib import contextmanager
  from typing import Any, Callable, Dict, Iterable, Iterator, List, Optional, Set, Sequence, Tuple
  import google.protobuf.descriptor_pb2
  from google.protobuf.compiler import plugin_pb2
  from google.protobuf.internal.containers import RepeatedCompositeFieldContainer
  from google.protobuf.internal.well_known_types import WKTBASES
  from .None import extensions_pb2
label_desc: Use image node_id 18 for calling the PkgWriter obj's underlying member method code with example usage: obj._import_casttype(casttype) and returns: self