code: def _serialize_icons(icons):
      
      toks = ['ICONS:', '<']
      for ic in icons:
          toks.extend(ic)
          # toks += [str(icon.left),
          #          icon.relation,
          #          str(icon.right)]
      toks += ['>']
      return ' '.join(toks)
docs: Serialize [IndividualConstraints] into the SimpleMRS encoding.