code: def _Device_mapVarIdx(self, mapping, done):
      """Map VarIdx in this Device table (if any) through mapping."""
      if id(self) in done:
          return
      done.add(id(self))
      if self.DeltaFormat == 0x8000:
          varIdx = mapping[(self.StartSize << 16) + self.EndSize]
          self.StartSize = varIdx >> 16
          self.EndSize = varIdx & 0xFFFF
  
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 10 for calling a global function with example usage: _Device_mapVarIdx(mapping, done) without return types