Do we need the class SeriesIdResolver?

[taojing2002]

In the SeriesIdResolver class, the method public static Identifier getPid(Identifier identifier) is used to get the Head identifier of a SID. The implementation of the method is to use the DataONE api call getSystemMetadata to get the Head identifier and it is hard to be replaced by Hashstore.
This method is only called in the class of ForesiteResourceMap. If we decide there are no SID in the resource map file, we may not need the method of SeriedsIdResolver.getPid at all.