StartTimeUnixNano is optional but strongly encouraged, see the
the detailed comments above Metric.
Value is UNIX Epoch time in nanoseconds since 00:00:00 UTC on 1 January
1970.
Generated from protobuf field <code>fixed64 start_time_unix_nano = 2;</code>
Type: start_time_unix_nano
File
vendor/open-telemetry/gen-otlp-protobuf/Opentelemetry/Proto/Metrics/V1/IntDataPoint.php, line 32