Long story short

The Hacking Multipart section on the Working with Multipart page, has an example that references a MultipartWriter.writer() method.

Expected behaviour

Methods referenced in documentation should exist. In this case it should be the MultipartWriter.write() method.

Actual behaviour

MultipartWriter.writer() method is referenced in documentation but does not exist

Steps to reproduce

1. Open Working with Multipart, CTRL+F for mpwriter.writer. mpwriter is a MultipartWriter object based on the example.
2. Open Multipart Reference. No references to the method.
3. Open multipart.py. No references to the method.

Your environment

aiohttp == 3.6.2