code: def undo_event(self, event):
      if self.pointer == 0:
          self.bell()
          return "break"
      cmd = self.undolist[self.pointer - 1]
      cmd.undo(self.delegate)
      self.pointer = self.pointer - 1
      self.can_merge = False
      self.check_saved()
      return "break"
  
imports: import string
  from idlelib.delegator import Delegator
label_desc: Use image node_id 14 for calling the UndoDelegator obj's underlying member method code with example usage: obj.undo_event(event) and returns: str, str