The file handle for the meta-data file. The meta-data file contains the number of replications as the first line, and the number of observations in each of the replications as the subsequent lines
Closes the data (.wdf) and metadata (.json) file handles, releasing them so the Welch files can be deleted (required on Windows). The metadata is flushed on write (autoflush), so this only releases the OS handles. Idempotent.