code: def _print_options_help(self):
      
      show_all_help = self._help_request.all_scopes
      if show_all_help:
        help_scopes = list(self._options.known_scope_to_info.keys())
      else:
        # The scopes explicitly mentioned by the user on the cmd line.
        help_scopes = set(self._options.scope_to_flags.keys()) - {GLOBAL_SCOPE}
  
      scope_infos = list(ScopeInfoIterator(self._options.known_scope_to_info).iterate(help_scopes))
      if scope_infos:
        for scope_info in scope_infos:
          help_str = self._format_help(scope_info)
          if help_str:
            print(help_str)
        return
      else:
        print(pants_release())
        print('\nUsage:')
        print('  ./pants [option ...] [goal ...] [target...]  Attempt the specified goals.')
        print('  ./pants help                                 Get help.')
        print('  ./pants help [goal]                          Get help for a goal.')
        print('  ./pants help-advanced [goal]                 Get help for a goal\'s advanced options.')
        print('  ./pants help-all                             Get help for all goals.')
        print('  ./pants goals                                List all installed goals.')
        print('')
        print('  [target] accepts two special forms:')
        print('    dir:  to include all targets in the specified directory.')
        print('    dir:: to include all targets found recursively under the directory.')
        print('\nFriendly docs:\n  http://pantsbuild.org/')
  
        print(self._format_help(ScopeInfo(GLOBAL_SCOPE, ScopeInfo.GLOBAL)))
docs: Print a help screen.
  
      Assumes that self._help_request is an instance of OptionsHelp.
  
      Note: Ony useful if called after options have been registered.