How to use the prospector.config.configuration.build_manager function in prospector

def get_parser():
    """
    This is a helper method to return an argparse parser, to
    be used with the Sphinx argparse plugin for documentation.
    """
    manager = cfg.build_manager()
    source = cfg.build_command_line_source(prog='prospector', description=None)
    return source.build_parser(manager.settings, None)

def _configure_prospector(self):
        # first we will configure prospector as a whole
        mgr = cfg.build_manager()
        config = mgr.retrieve(*cfg.build_default_sources())
        return config, mgr.arguments