code: def maxCtxFont(font):
      
  
      maxCtx = 0
      for tag in ('GSUB', 'GPOS'):
          if tag not in font:
              continue
          table = font[tag].table
          if table.LookupList is None:
              continue
          for lookup in table.LookupList.Lookup:
              for st in lookup.SubTable:
                  maxCtx = maxCtxSubtable(maxCtx, tag, lookup.LookupType, st)
      return maxCtx
docs: Calculate the usMaxContext value for an entire font.