issues: 754558237

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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
754558237 MDU6SXNzdWU3NTQ1NTgyMzc= 4635 Unexpected error when using `weighted` 14314623 closed 0     2 2020-12-01T16:49:39Z 2020-12-01T20:13:24Z 2020-12-01T20:13:24Z CONTRIBUTOR      

What happened: I just updated to the newest upstream master of xarray to branch of a pull request for #4625 and noticed a strange error in my regular workflow.

I am working with a dataset ds_transformed like this:

and when I try to apply a weighted mean with python transformed_ds.o2.weighted(transformed_ds.dz_t).mean('time')

I get the following error, which I do not understand:

```

TypeError Traceback (most recent call last) <ipython-input-101-b08fde69b74b> in <module> ----> 1 test = transformed_ds.o2.weighted(transformed_ds.dz_t).mean('time')

~/code/xarray/xarray/core/common.py in weighted(self, weights) 788 """ 789 --> 790 return self._weighted_cls(self, weights) 791 792 def rolling(

~/code/xarray/xarray/core/weighted.py in init(self, obj, weights) 121 _weight_check(weights.data) 122 --> 123 self.obj = obj 124 self.weights = weights 125

TypeError: descriptor 'obj' for 'Weighted' objects doesn't apply to a 'DataArrayWeighted' object ```

Using the synthetic example from #4625 this does not show up. I am wondering if anybody has an idea what could be wrong with my dataset that would cause this error?

Anything else we need to know?:

Environment:

Output of <tt>xr.show_versions()</tt> INSTALLED VERSIONS ------------------ commit: None python: 3.8.6 | packaged by conda-forge | (default, Oct 7 2020, 19:08:05) [GCC 7.5.0] python-bits: 64 OS: Linux OS-release: 3.10.0-1160.2.2.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.6 libnetcdf: 4.7.4 xarray: 0.16.3.dev2+ga41edc7.d20201201 pandas: 1.1.3 numpy: 1.19.2 scipy: 1.5.2 netCDF4: 1.5.4 pydap: None h5netcdf: 0.8.1 h5py: 2.10.0 Nio: None zarr: 2.4.0 cftime: 1.2.1 nc_time_axis: 1.2.0 PseudoNetCDF: None rasterio: 1.1.3 cfgrib: None iris: None bottleneck: None dask: 2.30.0 distributed: 2.30.0 matplotlib: 3.3.2 cartopy: 0.18.0 seaborn: None numbagg: None pint: 0.16.1 setuptools: 49.6.0.post20201009 pip: 20.2.4 conda: None pytest: 6.1.2 IPython: 7.18.1 sphinx: None 
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