id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1236356209,PR_kwDOAMm_X8431neg,6612,Typing for open_dataset/array/mfdataset and to_netcdf/zarr,43316012,closed,0,,,5,2022-05-15T18:09:15Z,2022-05-19T16:08:07Z,2022-05-17T19:32:01Z,COLLABORATOR,,0,pydata/xarray/pulls/6612,"<!-- Feel free to remove check-list items aren't relevant to your change -->

- [x] Closes #5382 

Mypy is not able to compute the overloads of to_netcdf properly (too many Unions).
I had to add some `# type: ignore`

I am not sure about the types of
* `concat_dim`
* `combine_attrs`: the `Callable` part is still with Anys","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6612/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull