public Attributes (ulong reserved)
Create a new empty `GckAttributes` array.
The returned set of attributes is floating, and should either be passed to another gck library function which consumes this floating reference, or if you wish to keep these attributes around you should ref them with ref_sink and unref them later with unref.
Should be set to always be [const
a floating reference to the new attributes array; when done with the array release it with unref.