fixes the missing type annotations

[wyli]

Is your feature request related to a problem? Please describe.
running the mypy commands

# python -m pip install -U -r requirements-dev.txt
./runtests.sh --mypy

generates the following warning messages, would be great to add type annotations to those functions.

monai/data/meta_obj.py:83:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/meta_obj.py:84:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/meta_obj.py:85:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/meta_obj.py:86:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/meta_tensor.py:372:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/transforms/intensity/dictionary.py:1589:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/transforms/intensity/dictionary.py:1662:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:292:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:293:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:613:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:614:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:944:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:945:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:1110:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:1111:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:1201:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/image_reader.py:1202:9: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
monai/data/dataset.py:1076:13: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
...

The warning is because functions that do not have any annotations (neither for any argument nor for the return type) are not type-checked

[f-schnabel]

Hi, I would like to work on this issue.

[f-schnabel]

@wyli I went through the code and fixed the MyPy warnings.
Some notes I would like your comment on:

1. I use a virtual environment where all the dependencies are placed into the venv/ folder. I've excluded this folder from mypy since otherwise it would find warnings in the dependencies. If you don't use a virtual environment, the exclusion should have no effect.
2. In some cases I had to change the implementation, since e.g. a variable is reassigned with a different type.
3. MyPy is still not checking all functions, only those that have type annotations. If you set the config check_untyped_defs = True there are still over 1000 warnings and errors. I would also like to tackle this task, should this be done in a separate issue or still be tracked in this?

[wyli]

all agreed, the PR looks great, and please feel free to create new tickets to track additional enhancements.