code: def get_connection(self, service_name):
          
          service = self.services.get(service_name, {})
          connection_class = service.get('connection', None)
  
          if not connection_class:
              msg = "Connection for '{0}' is not present in the cache."
              raise NotCached(msg.format(
                  service_name
              ))
  
          return connection_class
docs: Retrieves a connection class from the cache, if available.
  
          :param service_name: The service a given ``Connection`` talks to. Ex.
              ``sqs``, ``sns``, ``dynamodb``, etc.
          :type service_name: string
  
          :returns: A <kotocore.connection.Connection> subclass