code: function(source) {
  			// transform tokens
  			var tokens = this.lex(source), pos = 0, token;
  			for (var i = 0, il = tokens.length; i < il; i++) {
  				token = tokens[i];
  				token.start = pos;
  				token.end = (pos += token.value.length);
  			}
  			return tokens;
  		}
docs: Tokenizes CSS source. It's like `lex()` method,
  but also stores proper token indexes in source,
  so it's a bit slower
  @param {String} source
  @returns {Array}