':param theme: theme unique name'

def choose(self, theme_name):

    def recursive_update(widget):
        if hasattr(widget, 'set_theme_style'):
            widget.set_theme_style()
        for child in widget.children():
            if isinstance(child, QWidget):
                recursive_update(child)
    self.set_theme(theme_name)
    recursive_update(self._app)
