code: function isPctEncoded (chr) {
          if (!isPercentDigitDigit(chr, 0)) {
              return false;
          }
          var firstCharCode = parseHex2(chr, 1);
          var numBytes = utf8.numBytes(firstCharCode);
          if (numBytes === 0) {
              return false;
          }
          for (var byteNumber = 1; byteNumber < numBytes; byteNumber += 1) {
              if (!isPercentDigitDigit(chr, 3*byteNumber) || !utf8.isValidFollowingCharCode(parseHex2(chr, 3*byteNumber + 1))) {
                  return false;
              }
          }
          return true;
      }
docs: Returns whether or not the given char sequence is a correctly pct-encoded sequence.
  @param chr
  @return {boolean}