def record(amount)
      return if amount < 0
      @count.add_and_get(1)
      @total_amount.add_and_get(amount)
      @total_sq.add_and_get(amount * amount)
      @max.max(amount)
    end
def record(amount)
      return if amount < 0
      @count.add_and_get(1)
      @total_amount.add_and_get(amount)
      @total_sq.add_and_get(amount * amount)
      @max.max(amount)
    end
Initialize a new DistributionSummary instance with a given id
 Update the statistics kept by the summary with the specified amount.