Fix linting issues (#45)

* chore: fix black and isort comments

* chore: upgrade black to support Python 3.9

Author: aitorres

requirements-dev.txt

@@ -1,5 +1,5 @@
 -r requirements.txt
-black==20.8b-1
+black==21.10b0
 codecov==2.1.11
 django-stubs==1.7.0
 isort==5.7.0
@@ -13,5 +13,5 @@ pytest-mock==3.5.1
 python-multipart==0.0.5
 pytz==2019.3
 snapshottest==0.6.0
-typing-extensions==3.7.4.3
+typing-extensions==3.10.0.2
 tox==3.23.1