code: def seen(self, event, nickname):
          
          try:
              self.joined[nickname]
          except KeyError:
              pass
          else:
              if nickname == self.get_nickname(event):
                  prefix = "you are"
              else:
                  prefix = "%s is" % nickname
              return "%s here right now" % prefix
          try:
              seen = self.timesince(self.quit[nickname])
          except KeyError:
              return "%s has never been seen" % nickname
          else:
              return "%s was last seen %s ago" % (nickname,  seen)
docs: Shows the amount of time since the given nickname was last
          seen in the channel.