code: def get_possible_config_keys(self, action):
          
          keys = []
  
          # Do not write out the config options for writing out a config file
          if getattr(action, 'is_write_out_config_file_arg', None):
              return keys
  
          for arg in action.option_strings:
              if any([arg.startswith(2*c) for c in self.prefix_chars]):
                  keys += [arg[2:], arg] # eg. for '--bla' return ['bla', '--bla']
  
          return keys
docs: This method decides which actions can be set in a config file and
          what their keys will be. It returns a list of 0 or more config keys that
          can be used to set the given action's value in a config file.