module Snapshot:sig..end
val take : ?time:float -> Spacetime.Series.t -> unittake series takes a snapshot of the profiling annotations on the values
      in the minor and major heaps, together with GC stats, and write the
      result to the series file.  This function triggers a minor GC but does
      not allocate any memory itself.
      If the optional time is specified, it will be used instead of the
      result of Sys.time as the timestamp of the snapshot.  Such times
      should start from zero and be monotonically increasing.  This parameter
      is intended to be used so that snapshots can be correlated against wall
      clock time (which is not supported in the standard library) rather than
      elapsed CPU time.