code: def interpolateFromDeltas(self, varDataIndex, deltas):
      varData = self._varData
      scalars = [
          self._getScalar(ri)
          for ri in varData[varDataIndex].VarRegionIndex
      ]
      return self.interpolateFromDeltasAndScalars(deltas, scalars)
  
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 7 for calling the VarStoreInstancer obj's underlying member method code with example usage: obj.interpolateFromDeltas(varDataIndex, deltas) and returns: self