code: def set_limit(self, group, new_limit):
          
          if new_limit is None:
              self._group_limits.pop(group, None)
              return
  
          self._group_limits[group] = new_limit
docs: Set a new limit on the number of tasks in the `group`.
  
          :param group: Group key of the group to modify.
          :type group: hashable
          :param new_limit: New limit for the number of tasks running in `group`.
          :type new_limit: non-negative :class:`int` or :data:`None`
          :raise ValueError: if `new_limit` is non-positive
  
          The limit of tasks for the `group` is set to `new_limit`. If there are
          currently more than `new_limit` tasks running in `group`, those tasks
          will continue to run, however, the creation of new tasks is inhibited
          until the group is below its limit.
  
          If the limit is set to zero, no new tasks can be spawned in the group
          at all.
  
          If `new_limit` is negative :class:`ValueError` is raised instead.
  
          If `new_limit` is :data:`None`, the method behaves as if
          :meth:`clear_limit` was called for `group`.