docs: function (lastTypedKeys) {
                  var length = lastTypedKeys.length;
                  if (length <= 1) {
                      // It is useless to execute findLetterMatch in case lastTypedKeys contains only one character,
                      // because _findMatch has already done the job in that case
                      return -1;
                  }
                  // check that all the typed keys were the same:
                  var letter = lastTypedKeys.charAt(0);
                  for (var i = 1; i < length; i++) {
                      if (letter != lastTypedKeys.charAt(i)) {
                          return -1;
                      }
                  }
                  // look for a match for that key:
                  return this._findMatch(letter, true);
              }