code: def to_e164(name, origin=public_enum_domain, want_plus_prefix=True):
      
      if not origin is None:
          name = name.relativize(origin)
      dlabels = [d for d in name.labels if (d.isdigit() and len(d) == 1)]
      if len(dlabels) != len(name.labels):
          raise dns.exception.SyntaxError('non-digit labels in ENUM domain name')
      dlabels.reverse()
      text = ''.join(dlabels)
      if want_plus_prefix:
          text = '+' + text
      return text
docs: Convert an ENUM domain name into an E.164 number.
      @param name: the ENUM domain name.
      @type name: dns.name.Name object.
      @param origin: A domain containing the ENUM domain name.  The
      name is relativized to this domain before being converted to text.
      @type: dns.name.Name object or None
      @param want_plus_prefix: if True, add a '+' to the beginning of the
      returned number.
      @rtype: str