def _get_extractor(config_dict):
extractor = None<EOL>extract_config = None<EOL>for key, value in config_dict.items():<EOL><INDENT>if key in EXTRACTORS:<EOL><INDENT>return parse_extractor(key, value)<EOL><DEDENT><DEDENT>else:  <EOL><INDENT>raise Exception(<EOL>'<STR_LIT>'.format(config_dict))<EOL><DEDENT>
Utility function, get an extract function for a single valid extractor name in config
        and error if more than one or none