new_async
Description:
[ CCode ( finish_name = "g_async_initable_new_finish" ) ]
public static async Object new_async (Type object_type, int io_priority = DEFAULT, Cancellable? cancellable, ...) throws Error
  public static async Object new_async (Type object_type, int io_priority = DEFAULT, Cancellable? cancellable, ...) throws Error
Helper function for constructing AsyncInitable object.
This is similar to @new but also initializes the object asynchronously.
When the initialization is finished, callback will be called. You can then call new_async.end 
      to get the new object and check for any errors.
Parameters:
| object_type | a Type supporting AsyncInitable. | 
| io_priority | the I/O priority of the operation | 
| cancellable | optional Cancellable object, null to ignore. | 
| ... | the value of the first property, followed by other property value pairs, and ended by null. | 
| callback | a TaskReadyCallback to call when the initialization is finished | 
| first_property_name | the name of the first property, or null if no properties | 
| user_data | the data to pass to callback function |