Method replaceNanWithNull

src/danfojs-base/shared/utils.ts:694–703

* Replace NaN with null before tensor operations * @param arr

(arr: ArrayType1D | ArrayType2D)

     * @param arr
     */
    replaceNanWithNull(arr: ArrayType1D | ArrayType2D) {
        const values = arr.map((val) => {
            if (isNaN(val as unknown as number)) {
                return null;
            } else {
                return val;
            }
        });
        return values;
    }

    /**
     * Get duplicate values in a array