Importing modules

i made a module just like you did in the video but when i import it, it gives me an error like this:
~\hello.py in
16 {
17 “cell_type”: “code”,
—> 18 “execution_count”: null,
19 “metadata”: {},
20 “outputs”: [],

NameError: name ‘null’ is not defined

what do i do?

plz post the complete code