Get get configuration of the specified rate limiter

        :param str service:
          rate limiter name

        :param config:
          optional global rate limiters configuration.
          If not specified, then use rate limiters configuration
          specified at application level

def get_config(cls, service, config=None):
        """Get get configuration of the specified rate limiter

        :param str service:
          rate limiter name

        :param config:
          optional global rate limiters configuration.
          If not specified, then use rate limiters configuration
          specified at application level
        """
        config = config or cls.get_configs()
        return config[service]