code: func (api *PrivateLightServerAPI) SetClientCapacity(id enode.ID, cap uint64) error {
  	if cap != 0 && cap < minCapacity {
  		return ErrMinCap
  	}
  	return api.server.priorityClientPool.setClientCapacity(id, cap)
  }
docs: // SetClientCapacity sets the priority capacity assigned to a given client.
  // If the assigned capacity is bigger than zero then connection is always
  // guaranteed. The sum of capacity assigned to priority clients can not exceed
  // the total available capacity.
  //
  // Note: assigned capacity can be changed while the client is connected with
  // immediate effect.