code: def add_update_callback(self, group=None, name=None, cb=None):
          
          if not group and not name:
              self.all_update_callback.add_callback(cb)
          elif not name:
              if group not in self.group_update_callbacks:
                  self.group_update_callbacks[group] = Caller()
              self.group_update_callbacks[group].add_callback(cb)
          else:
              paramname = '{}.{}'.format(group, name)
              if paramname not in self.param_update_callbacks:
                  self.param_update_callbacks[paramname] = Caller()
              self.param_update_callbacks[paramname].add_callback(cb)
docs: Add a callback for a specific parameter name. This callback will be
          executed when a new value is read from the Crazyflie.