code: def build(cls, keys, down=None):
          
          codes = []
          for key in keys.split('-'):
              key = keycode(key)
              codes.append(key)
  
          events = []
          if down is None or down:
              for code in codes:
                  events.append(cls(code, down=True))
  
          if down is None or not down:
              for code in reversed(codes):
                  events.append(cls(code, down=False))
          return events
docs: Build a key combination, such as:
  
          ctrl-t