class_docstr: Inherit from this class if you wish to override any of the stages below. Otherwise, use
  ``argcomplete.autocomplete()`` directly (it's a convenience instance of this class). It has the same signature as
  :meth:`CompletionFinder.__call__()`.
code: def _get_subparser_completions(self, parser, cword_prefix):
      aliases_by_parser: Dict[argparse.ArgumentParser, List[str]] = {}
      for key in parser.choices.keys():
          p = parser.choices[key]
          aliases_by_parser.setdefault(p, []).append(key)
  
      for action in parser._get_subactions():
          for alias in aliases_by_parser[parser.choices[action.dest]]:
              if alias.startswith(cword_prefix):
                  self._display_completions[alias] = action.help or ""
  
      completions = [
          subcmd
          for subcmd in parser.choices.keys()
          if subcmd.startswith(cword_prefix)
      ]
      return completions
  
imports: import argparse
  import os
  import sys
  from collections.abc import Mapping
  from typing import Callable, Dict, List, Optional, Sequence, Union
  from .None import io
  from .completers import ChoicesCompleter, FilesCompleter, SuppressCompleter
  from .io import debug, mute_stderr
  from .lexers import split_line
  from .packages._argparse import IntrospectiveArgumentParser, action_is_greedy, action_is_open, action_is_satisfied
label_desc: Use image node_id 5 for calling the CompletionFinder obj's underlying member method code with example usage: obj._get_subparser_completions(parser, cword_prefix) and returns: completions