Retrieves the gtk.constraint_target.ConstraintTarget used as the source for the constraint.
If the source is set to NULL at creation, the constraint will use the widget using the gtk.constraint_layout.ConstraintLayout as the source.
the source of the constraint
Retrieves the gtk.constraint_target.ConstraintTarget used as the source for the constraint.
If the source is set to NULL at creation, the constraint will use the widget using the gtk.constraint_layout.ConstraintLayout as the source.