code: public ServiceFuture<HybridConnectionKeyInner> listHybridConnectionKeysAsync(String resourceGroupName, String name, String namespaceName, String relayName, final ServiceCallback<HybridConnectionKeyInner> serviceCallback) {
          return ServiceFuture.fromResponse(listHybridConnectionKeysWithServiceResponseAsync(resourceGroupName, name, namespaceName, relayName), serviceCallback);
      }
docs: Get the send key name and value of a Hybrid Connection.
  Get the send key name and value of a Hybrid Connection.
  
  @param resourceGroupName Name of the resource group to which the resource belongs.
  @param name Name of the App Service plan.
  @param namespaceName The name of the Service Bus namespace.
  @param relayName The name of the Service Bus relay.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object