issues: 434444058

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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
434444058 MDExOlB1bGxSZXF1ZXN0MjcxNDM1NjU4 2904 Minor improvement of docstring for Dataset 691772 closed 0     6 2019-04-17T19:16:50Z 2019-04-17T20:09:26Z 2019-04-17T20:08:46Z CONTRIBUTOR   0 pydata/xarray/pulls/2904

This might help to avoid confusion. data_vars is always a mapping, not a mapping, a variable or a tuple.

Passing just a tuple, does not work of course. But for xarray newbies, this might be less obvious and the error message is also not easy to interpret: ```

xr.Dataset(('dim1', np.ones(5))) ... TypeError: unhashable type: 'numpy.ndarray' ```

The correct version of the example above should be: ```

xr.Dataset({'myvar': ('dim1', np.ones(5))})
<xarray.Dataset> Dimensions: (dim1: 5) Dimensions without coordinates: dim1 Data variables: myvar (dim1) float64 1.0 1.0 1.0 1.0 1.0 ```

 
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