/**
* Creates a clone of the input (or <b>this</b>) object. <br>
* To avoid unexpected results, one should not use this function to clone <b>arrays</b>.<br>
* If you want to be able to clone object with <b>null</b> prototype, remove the 
* corresponding statement below (see the comments).
* @method clone
* @param {Object} obj
* @returns {Object|Boolean} Returns a new object or false if the input value is not a valid object.
*/
clone: function (obj) {
    var donor;
    if (obj) {
        if (typeof obj !== 'object') {
            return false; // not an object
        }
        donor = obj;
    } else {
        donor = this;
    }
    if (!donor.__proto__) { // remove this statement to be able to clone object with __proto__ === null
        return false; // has not prototype
    }
    if (typeof donor.__proto__ !== 'object') {
        return false; // prototype is not an object
    }
    let result = Object.create(donor.__proto__);
    for (let key in donor) {
        if (!donor.hasOwnProperty(key)) {
            continue;
        }
        result[key] = donor[key];
    }
    return result;
}