So I've recently ran into this issue, and I believe I found a cleaner way to import your layers.

First for the structure of the zip file which you upload:

• You do not need an __init__.py file
• Put all the scripts which you want to import into a folder name python
• Zip up that python folder (choose any name you want) and upload it to your layer
• Once uploaded, and the layer has been configured in your lambda function, you can simply use it with import {filename}

So if your script in the python folder was called something like custom_helper.py, import it in your lambda with import custom_helper.

I am not sure if this is the clean way to do it, but it seems simple enough to start.