## Description

Attempting to use Celery in a mypy enabled project we found that errors in Celery's type annotations prevent mypy running against our code. Basically this https://stackoverflow.com/questions/68114378/mypy-crashes-due-to-syntax-error-in-underlying-modules situation 

This branch doesn't attempt to fully overhaul the annotations; it just makes it possible to 

```
from celery import Celery
from celery.schedules import crontab
```
successfully.
Correct some mypy errors. ## Description

Attempting to use Celery in a mypy enabled project we found that errors in Celery's type annotations prevent mypy running against our code. Basically this https://stackoverflow.com/questions/68114378/mypy-crashes-due-to-syntax-error-in-underlying-modules situation 

This branch doesn't attempt to fully overhaul the annotations; it just makes it possible to 

```
from celery import Celery
from celery.schedules import crontab
```
successfully.
.DS_Store
*.pyc
*$py.class
*~
.*.sw[pon]
dist/
*.egg-info
*.egg
*.egg/
*.eggs/
build/
.build/
_build/
pip-log.txt
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erl_crash.dump
*.db
Documentation/
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.ropeproject/
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.idea/
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celery/tests/cover/
.ve*
cover/
.vagrant/
.cache/
htmlcov/
coverage.xml
test.db
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.DS_Store
*.pyc
*$py.class
*~
.*.sw[pon]
dist/
*.egg-info
*.egg
*.egg/
*.eggs/
build/
.build/
_build/
pip-log.txt
.directory
erl_crash.dump
*.db
Documentation/
.tox/
.ropeproject/
.project
.pydevproject
.idea/
.coverage
celery/tests/cover/
.ve*
cover/
.vagrant/
.cache/
htmlcov/
coverage.xml
test.db
.git/
