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
816016031,MDU6SXNzdWU4MTYwMTYwMzE=,4955,set_index does not respect keep_attrs,31640292,closed,0,,,2,2021-02-25T02:22:05Z,2022-03-17T17:11:41Z,2022-03-17T17:11:41Z,CONTRIBUTOR,,,,"
**What happened**: set_index removes attributes from a coordinate, even with `xr.set_options(keep_attrs=True)`

**What you expected to happen**: The attributes to be preserved through the coordinate renaming

**Minimal Complete Verifiable Example**:

```python
import xarray as xr
xr.set_options(keep_attrs=True)
x = xr.DataArray([1,2], dims=['x'])
x.coords['x'] = (['x'],[2,3], {""name"":""coord_1""})
x.coords['a'] = (['x'],[0,1], {""name"":""coord 2""})
x.set_index(x='a').x.attrs # should be {""name"":""coord 2""}, is {}
```

**Environment**:

<details><summary>Output of <tt>xr.show_versions()</tt></summary>

INSTALLED VERSIONS
------------------
commit: None
python: 3.8.5 | packaged by conda-forge | (default, Sep 24 2020, 16:55:52) 
[GCC 7.5.0]
python-bits: 64
OS: Linux
OS-release: 3.10.0-1160.11.1.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en.UTF-8
LOCALE: None.None
libhdf5: 1.10.6
libnetcdf: 4.7.4

xarray: 0.16.2
pandas: 1.2.0
numpy: 1.19.1
scipy: 1.6.0
netCDF4: 1.5.5.1
pydap: None
h5netcdf: 0.8.1
h5py: 3.1.0
Nio: None
zarr: None
cftime: 1.3.1
nc_time_axis: 1.2.0
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: 1.3.2
dask: 2021.01.0
distributed: 2021.01.0
matplotlib: 3.3.3
cartopy: 0.18.0
seaborn: 0.11.1
numbagg: None
pint: 0.16.1
setuptools: 49.6.0.post20210108
pip: 20.2.3
conda: None
pytest: None
IPython: 7.18.1
sphinx: 3.4.3


</details>
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742656246,MDExOlB1bGxSZXF1ZXN0NTIwNzM4NDky,4582,Match all float types in formatitem,31640292,closed,0,,,5,2020-11-13T17:53:12Z,2020-11-15T23:07:35Z,2020-11-15T21:30:01Z,CONTRIBUTOR,,0,pydata/xarray/pulls/4582,"This is a simple change to format_item in core/formatting.py that allows other float type (e.g. numpy.float16, numpy.float32) to be formatted the same as any other float.

 - [x] Partially Addresses #4575
 - [x] Passes `isort . && black . && mypy . && flake8`
 - [x] Tests added

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