iter_parent
Description:
Sets iter to be the parent of child.
If child is at the toplevel, and doesn’t have a parent, then iter is set to an invalid iterator and 
      false is returned. child will remain a valid node after this function has been called.
iter will be initialized before the lookup is performed, so child and iter cannot point to the same 
      memory location.
Parameters:
| this | 
           a `GtkTreeModel`  | 
      
| iter | 
           the new `GtkTreeIter` to set to the parent  | 
      
| child | 
           the `GtkTreeIter`  | 
      
Returns:
| 
           true, if   |