Update to mypy 0.9

[ascillitoe]

Update to mypy 0.900. This is a precursor to #605.

This PR is similar to SeldonIO/alibi-detect#490, but with a few extra changes:

• In explainers/cfproto.py two lines that previously raised type-var arguments are now raising arg-type errors, so the type: ignore's have been updated to ignore these. arg-type errors seem logical to me here, but I might be missing something.

• The second call to ray.remote() below:

  DistributedAnchorTabular.ray.remote(RemoteSampler).remote(
                      *(train_data_id, d_train_data_id, sampler)

  results in the error:

  No overload variant of "remote" of "RemoteFunction" matches argument type "Tuple[Any, Any, TabularSampler]"
  

  This doesn't seem surprising since the overloaded type sigs are all similar to:

  def remote(self, arg0: Optional[ObjectRef[None]])
  

  i.e. ObjectRef's are always expected, rather than Any. I don't have an answer for why mypy<0.9 doesn't pick this up though... To avoid an error, type: ignore[call-overload] is added.

[ascillitoe]

@jklaise @mauicv any thoughts on the new type: ignore's detailed above?

[codecov]

Codecov Report

Merging #638 (cce2108) into master (27706c7) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #638      +/-   ##
==========================================
- Coverage   82.06%   81.96%   -0.10%     
==========================================
  Files          77       77              
  Lines       10519    10519              
==========================================
- Hits         8632     8622      -10     
- Misses       1887     1897      +10     

Impacted Files	Coverage Δ
alibi/explainers/anchor_tabular.py	78.72% <ø> (ø)
alibi/explainers/cfproto.py	75.53% <100.00%> (ø)
alibi/explainers/anchor_base.py	84.81% <0.00%> (-2.54%)	⬇️
alibi/explainers/ale.py	59.79% <0.00%> (-0.51%)	⬇️
alibi/utils/distributed.py	67.11% <0.00%> (-0.45%)	⬇️

[jklaise]

LGTM. I would wager that the type-var to arg-type error was a bug in the older version of mypy.

[ascillitoe]

I would wager that the type-var to arg-type error was a bug in the older version of mypy.

Yeh agreed, arg-type does make more sense for those lines.