code: def getUsedPoints(self):
      # Empty set means "all points used".
      if None not in self.coordinates:
          return frozenset()
      used = frozenset(
          [i for i, p in enumerate(self.coordinates) if p is not None]
      )
      # Return None if no points used.
      return used if used else None
  
imports: from fontTools.misc.fixedTools import fixedToFloat, floatToFixed, floatToFixedToStr, strToFixedToFloat, otRound
  from fontTools.misc.textTools import safeEval
  import array
  from collections import Counter, defaultdict
  import io
  import logging
  import struct
  import sys
label_desc: Use image node_id 4 for calling the TupleVariation obj's underlying member method code with example usage: obj.getUsedPoints() and returns: unknown, frozenset