def min_time_next
      tn = DEVS::INFINITY
      if (obj = @scheduler.peek)
        tn = obj.time_next
      end
      tn
    end
def min_time_next
      tn = DEVS::INFINITY
      if (obj = @scheduler.peek)
        tn = obj.time_next
      end
      tn
    end
Returns the minimum time next in all children

 @return [Numeric] the min time next