Setting a custom time field for metrics

[jgericke]

Hi,

Is there any recommended approach in setting a metric's timestamp to a custom value?

I see there is reference to the timestamp field within the Collector class docstring but this doesn't appear to be exposed anywhere or settable.

    **Samples**

    Samples form the actual time series data. Each sample consists of:

      - a float64 value
      - a millisecond-precision timestamp

Understandably setting a custom timestamp isn't preferable from a Prometheus perspective, but I have a bit of a weird usecase.

Regards
Jules