isSymmetric() {
                if (this.isSquare()) {
                    for (var i = 0; i < this.rows; i++) {
                        for (var j = 0; j <= i; j++) {
                            if (this.get(i, j) !== this.get(j, i)) {
                                return false;
                            }
                        }
                    }
                    return true;
                }
                return false;
            }
@return {boolean} true if the matrix is square and has the same values on both sides of the diagonal