Set ``self.``:meth:`get_top_widget` transient for
        ``parent_view.get_top_widget()``.

def set_parent_view(self, parent_view):
        """
        Set ``self.``:meth:`get_top_widget` transient for
        ``parent_view.get_top_widget()``.
        """
        top = self.get_top_widget()
        if isinstance(top, (list, tuple)):
            for t in top:
                if t is not None:
                    t.set_transient_for(parent_view.get_top_widget())
        elif top is not None:
            top.set_transient_for(parent_view.get_top_widget())