Obtain the list of attribute namespaces where new attributes
can be created by a user. An example of this is extended
attributes (in the "xattr" namespace).
If cancellable is not NULL, then the operation can be cancelled by
triggering the cancellable object from another thread. If the operation
was cancelled, the error G_IO_ERROR_CANCELLED will be returned.
Obtain the list of attribute namespaces where new attributes can be created by a user. An example of this is extended attributes (in the "xattr" namespace). If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned.