<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def on_top_level_changed(self, top_level):
 """Actions to perform when a plugin is undocked to be moved."""

        if top_level:
            self.undock_action.setDisabled(True)
        else:
            self.undock_action.setDisabled(False)