# File lib/new_relic/rack/developer_mode/segment_summary.rb, line 20
        def <<(segment)
          if metric_name != segment.metric_name
            raise ArgumentError, "Metric Name Mismatch: #{segment.metric_name} != #{metric_name}"
          end

          # a nested segment should use the sum of the top level totals
          @total_time += segment.duration if current_nest_count == 0
          @exclusive_time += segment.exclusive_duration
          @call_count += 1
        end