TYP: pd.isna
Inferred by mypy and pyright:
```py
import numpy as np
import pandas as pd

class A:
    ...

# bool
reveal_type(pd.isna(1))

# npt.NDArray[np.bool_]
reveal_type(pd.isna([]))
reveal_type(pd.isna(np.zeros(3)))
reveal_type(pd.isna(pd.DatetimeIndex([None])))

# pd.DataFrame
reveal_type(pd.isna(pd.DataFrame()))

# pd.Series
reveal_type(pd.isna(pd.Series()))

# Union of all possible cases
reveal_type(pd.isna(A())) # should be bool
```

Would you mind not force pushing the branch  in the future?  It makes it hard to see what changes you made in just the last commit. > Would you mind not force pushing the branch in the future? It makes it hard to see what changes you made in just the last commit.

Okay. was rebasing on main (git pull --rebase main) but kept the new commit separate. > > Would you mind not force pushing the branch in the future? It makes it hard to see what changes you made in just the last commit.
> 
> Okay. was rebasing on main (git pull --rebase main) but kept the new commit separate.

I just do
```
git fetch upstream
git merge upstream/main
git add the_files_I_changed
git commit -m "why I changed those files"
git push origin mybranch
```
That seems to make it easier to track things for others.
 @twoertwein I approved, but I think @simonjayhawkins or @jbrockmendel should take a look as well. @twoertwein if you can merge master green, except for mypy error also present on main thanks @twoertwein 