code: def postscriptBlueScaleFallback(info):
      
      blues = getAttrWithFallback(info, "postscriptBlueValues")
      otherBlues = getAttrWithFallback(info, "postscriptOtherBlues")
      maxZoneHeight = 0
      blueScale = 0.039625
      if blues:
          assert len(blues) % 2 == 0
          for x, y in zip(blues[:-1:2], blues[1::2]):
              maxZoneHeight = max(maxZoneHeight, abs(y-x))
      if otherBlues:
          assert len(otherBlues) % 2 == 0
          for x, y in zip(otherBlues[:-1:2], otherBlues[1::2]):
              maxZoneHeight = max(maxZoneHeight, abs(y-x))
      if maxZoneHeight != 0:
          blueScale = 3/(4*maxZoneHeight)
      return blueScale
docs: Fallback to a calculated value: 3/(4 * *maxZoneHeight*)
      where *maxZoneHeight* is the tallest zone from *postscriptBlueValues*
      and *postscriptOtherBlues*. If zones are not set, return 0.039625.