When a dict is updated with update(), instead of return None, it will return the updated dict.

example: 

>>> a = {"test": 1}
>>> b = {"type": 2}
>>> c = a.update(b)
>>> print(c)
{"test": 1, "type": 1}

Can you please print the output of python -v? Using python 3.8.0 on Linux returns None for update method.

Python 3.9.0a5+ (heads/master:c606624af8, Apr 18 2020, 18:42:51)
[Clang 11.0.3 (clang-1103.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> a = {"test": 1}
>>> b = {"type": 2}
>>> c = a.update(b)
>>> print(c)
None

on macOS master branch, the issue is not reproducible.

Python 3.8.2+ (heads/3.8:c496e29c2b, Apr 18 2020, 21:42:41)
[Clang 11.0.3 (clang-1103.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> a = {"test": 1}
>>> b = {"type": 2}
>>> c = a.update(b)
>>> print(c)
None

This looks like a proposed "enhancement" rather than a bug report. Unfortunately, this is not possible for a myriad of reasons, from backward compatibility to overall use of mutating methods in Python.