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
558977158,MDU6SXNzdWU1NTg5NzcxNTg=,3743,A suggested solution to the `TypeError: Invalid value for attr:` error upon `.to_netcdf`,6872529,open,0,,,3,2020-02-03T10:10:51Z,2023-04-06T17:43:37Z,,NONE,,,,"Even though netcdf conventions don't allow some data types in the attributes, it might be usefull to simply serialize those as strings rather than throw an error. Maybe add a `force_serialization` keyword argument to the `.to_netcdf` method.

Example:
Setup a DataArray with _bad values_ in the attributes:
```python
import numpy as np
from xarray import DataArray, load_dataset
from pandas import Timestamp

from numbers import Number

valid_types = (str, Number, np.ndarray, np.number, list, tuple)

da = DataArray(
    name='bad_values',
    attrs=dict(
        bool_value=True,
        none_value=None,
        datetime_value=Timestamp.now()
    )
)

ds = da.to_dataset()
ds.bad_values.attrs
```

Output:
```python
{'bool_value': True,
 'none_value': None,
 'datetime_value': Timestamp('2020-02-03 10:53:02.350105')}
```

The code in the except clause can be easily impolemented under [`_validate_attrs`](https://github.com/pydata/xarray/blob/4c96d53e6caa78d56b785f4edee49bbd4037a82f/xarray/backends/api.py#L185).

```python
try:
    ds.to_netcdf('test.nc')
    # Fails with TypeError: Invalid value for attr: ...
except TypeError as e:
    print(e.__class__.__name__, e)
    for variable in ds.variables.values():
        for k, v in variable.attrs.items():
            if not isinstance(v, valid_types) or isinstance(v, bool):
                variable.attrs[k] = str(v)

    ds.to_netcdf('test.nc')  # Works as expected

ds_from_file = load_dataset('test.nc')
ds_from_file.bad_values.attrs
```

Output:
```python
TypeError Invalid value for attr: None must be a number, a string, an ndarray or a list/tuple of numbers/strings for serialization to netCDF files

{'bool_value': 'True',
 'none_value': 'None',
 'datetime_value': '2020-02-03 10:43:38.479866'}
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3743/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue