function append(arg1, arg2) {
        // disregard undefined args
        if (typeof arg1 === 'undefined') {
            return arg2;
        }
        if (typeof arg2 === 'undefined') {
            return arg1;
        }
        // if either argument is not an array, make it so
        if (!Array.isArray(arg1)) {
            arg1 = createSequence(arg1);
        }
        if (!Array.isArray(arg2)) {
            arg2 = [arg2];
        }
        return arg1.concat(arg2);
    }
Append second argument to first
@param {Array|Object} arg1 - First argument
@param {Array|Object} arg2 - Second argument
@returns {*} Appended arguments