3387 Fix 0.0 or None value in AsDiscrete

[Nic-Ma]

Fixes #3387 .

Description

This PR fixed the None or 0.0 value of to_onehot and threshold at runtime.

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[Nic-Ma]

Hi @yiheng-wang-nv ,

Please note that, we don't support the case that: set the to_onehot or threshold not to None at init(), and set the to_onehot or threshold to None at call() to disable the ToOneHot or Threshold actions.
It can only support to enable the action at runtime.
I think it's same as all the align_corners arg of call() in the spatial transforms:
https://github.com/Project-MONAI/MONAI/blob/dev/monai/transforms/spatial/array.py#L552

Thanks.

[Nic-Ma]

/black

[Nic-Ma]

/build

[yiheng-wang-nv]

Thanks @Nic-Ma