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
28575097,MDU6SXNzdWUyODU3NTA5Nw==,32,Dataset.__delitem__() kills dimensions dictionary,6509590,closed,0,,,5,2014-03-02T07:48:33Z,2014-03-07T06:15:36Z,2014-03-07T06:15:36Z,NONE,,,,"Trying to re-align slocum with xray... it seems that deleting a variable from a Dataset object erases the dimensions dictionary:

```
In [47]: fcst.dimensions
Out[47]: Frozen(OrderedDict([(u'lat', 9), (u'lon', 9), (u'height_above_ground4', 1), (u'time', 65)]))

In [48]: del fcst['height_above_ground4']

In [49]: fcst.dimensions
Out[49]: Frozen(OrderedDict())
```

Also, the removed variable still appears as a dimension in the remaining variables' coordinate systems:

```
In [57]: fcst.variables
Out[57]: Frozen(_VariablesDict([(u'lat', <xray.XArray (lat: 9): object>), (u'lon', <xray.XArray (lon: 9): object>), (u'time', <xray.XArray (time: 65): datetime64[ns]>), (u'u-component_of_wind_height_above_ground', <xray.XArray (time: 65, height_above_ground4: 1, lat: 9, lon: 9): float32>), (u'v-component_of_wind_height_above_ground', <xray.XArray (time: 65, height_above_ground4: 1, lat: 9, lon: 9): float32>)]))
```

Is this intentional? I'm using **delitem** as replacement for the old polyglot's Dataset.squeeze() - perhaps that's abuse?
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