code: def register(self, correlation_id, key, connection):
          
          item = DiscoveryItem()
          item.key = key
          item.connection = connection
          self._items.append(item)
docs: Registers connection parameters into the discovery service.
  
          :param correlation_id: (optional) transaction id to trace execution through call chain.
  
          :param key: a key to uniquely identify the connection parameters.
  
          :param connection: a connection to be registered.