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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def delete(cls, label='default', path=None):
 """Delete a server configuration. This method is thread safe. :param label: A string. The configuration identified by ``label`` is deleted. :param path: A string. The configuration file to be manipulated. Defaults to what is returned by :func:`nailgun.config._get_config_file_path`. :returns: ``None`` """

        if path is None:
            path = _get_config_file_path(
                cls._xdg_config_dir,
                cls._xdg_config_file
            )
        cls._file_lock.acquire()
        try:
            with open(path) as config_file:
                config = json.load(config_file)
            del config[label]
            with open(path, 'w') as config_file:
                json.dump(config, config_file)
        finally:
            cls._file_lock.release()