isApproximatelyEqualTo(obj, epsilon) {
        if (!(obj instanceof Rect)) {
            return false;
        }
        /** @type {Rect!} */
        let other = obj;
        return Math.abs(other.x - this.x) <= epsilon &&
            Math.abs(other.y - this.y) <= epsilon &&
            Math.abs(other.right() - this.right()) <= epsilon &&
            Math.abs(other.bottom() - this.bottom()) <= epsilon;
    }
@param {!Rect|*} obj
@param {!number} epsilon
@returns {!boolean}