docs: def add_client(self, user_id=None):
          """
          Adds current instance to public or private channel.
          If user_id is specified it will be added to the private channel,
          If user_id is not specified it will be added to the public one instead.
          """
          if user_id is None:
              # generate a random uuid if it's an unauthenticated client
              self.channel = 'public'
              user_id = uuid.uuid1().hex
          else:
              self.channel = 'private'
          
          self.id = user_id
          self.channels[self.channel][self.id] = self
          print 'Client connected to the %s channel.' % self.channel