code: def storeDeltas(self, deltas, *, round=round):
      deltas = [round(d) for d in deltas]
      if len(deltas) == len(self._supports) + 1:
          deltas = tuple(deltas[1:])
      else:
          assert len(deltas) == len(self._supports)
          deltas = tuple(deltas)
  
      varIdx = self._cache.get(deltas)
      if varIdx is not None:
          return varIdx
  
      if not self._data:
          self._add_VarData()
      inner = len(self._data.Item)
      if inner == 0xFFFF:
          # Full array. Start new one.
          self._add_VarData()
          return self.storeDeltas(deltas)
      self._data.addItem(deltas, round=noRound)
  
      varIdx = (self._outer << 16) + inner
      self._cache[deltas] = varIdx
      return varIdx
  
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 OnlineVarStoreBuilder obj's underlying member method code with example usage: obj.storeDeltas(deltas) and returns: varIdx, varIdx, self