code: def finish(self, optimize=True):
      self._regionList.RegionCount = len(self._regionList.Region)
      self._store.VarDataCount = len(self._store.VarData)
      for data in self._store.VarData:
          data.ItemCount = len(data.Item)
          data.calculateNumShorts(optimize=optimize)
      return self._store
  
imports: from fontTools.misc.roundTools import noRound, otRound
  from fontTools.misc.intTools import bit_count
  from fontTools.ttLib.tables import otTables
  from fontTools.varLib.models import supportScalar
  from fontTools.varLib.builder import buildVarRegionList, buildVarStore, buildVarRegion, buildVarData
  from functools import partial
  from collections import defaultdict
  from heapq import heappush, heappop
label_desc: Use image node_id 4 for calling the OnlineVarStoreBuilder obj's underlying member method code with example usage: obj.finish(optimize) and returns: self