class_docstr: This is an argparse Action that will raise an exception in
  order to skip the rest of the argument parsing when --help is passed.
  This prevents argparse from quitting due to missing required arguments
  when any are defined, for example by ``pytest_addoption``.
  This is similar to the way that the builtin argparse --help option is
  implemented by raising SystemExit.
class_docstr_tok: ["This","is","an","argparse","Action","that","will","raise","an","exception","in","order","to","skip","the","rest","of","the","argument","parsing","when","--","help","is","passed",".","This","prevents","argparse","from","quitting","due","to","missing","required","arguments","when","any","are","defined",",","for","example","by","``","pytest_addoption","``",".","This","is","similar","to","the","way","that","the","builtin","argparse","--","help","option","is","implemented","by","raising","SystemExit","."]
code: def __call__(self, parser, namespace, values, option_string=None):
      setattr(namespace, self.dest, self.const)
  
      # We should only skip the rest of the parsing after preparse is done
      if getattr(parser._parser, "after_preparse", False):
          raise PrintHelp
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import sys
  from argparse import Action
  import py
  import pytest
  from _pytest.config import PrintHelp
label_desc: Use image node_id 2 for calling the HelpAction obj's underlying member method code with example usage: obj.__call__(parser, namespace, values, option_string) without return types