175     auto sum = [](const uint64_t& l, const uint64_t& r) -> uint64_t {  in operator +=()  local
180     numReadsCompleted = sum(numReadsCompleted, rhs.numReadsCompleted);  in operator +=()
181     numReadsMerged = sum(numReadsMerged, rhs.numReadsMerged);  in operator +=()
182     numKibRead = sum(numKibRead, rhs.numKibRead);  in operator +=()
183     readTimeInMs = sum(readTimeInMs, rhs.readTimeInMs);  in operator +=()
184     numWritesCompleted = sum(numWritesCompleted, rhs.numWritesCompleted);  in operator +=()
185     numWritesMerged = sum(numWritesMerged, rhs.numWritesMerged);  in operator +=()
186     numKibWritten = sum(numKibWritten, rhs.numKibWritten);  in operator +=()
187     writeTimeInMs = sum(writeTimeInMs, rhs.writeTimeInMs);  in operator +=()
188     totalIoTimeInMs = sum(totalIoTimeInMs, rhs.totalIoTimeInMs);  in operator +=()
189     weightedTotalIoTimeInMs = sum(weightedTotalIoTimeInMs, rhs.weightedTotalIoTimeInMs);  in operator +=()
190     numFlushCompleted = sum(numFlushCompleted, rhs.numFlushCompleted);  in operator +=()
191     flushTimeInMs = sum(flushTimeInMs, rhs.flushTimeInMs);  in operator +=()