IndexSlice cannot infer missing values when an Index object is passed in
Here is the code snippet:

```python
import pandas as pd

df = pd.DataFrame({'id': [1,2,3,4,5], 
                   'age':[22,21,23,24,25], 
                   'sex':['M','F','M','F','M'],
                   'height':[165,152,166,154,176]
                  })

df = df.set_index(['id','age','sex'])
i = pd.Index([1,2,3])

df.loc[pd.IndexSlice[i, 21,], ['height']] # TypeError: unhashable type: 'Int64Index'
df.loc[pd.IndexSlice[i, 21,:], ['height']] # works
df.loc[pd.IndexSlice[[1,2,3], 21,], ['height']] # works
```

If an `Index` object is passed into the `IndexSlice` object, it cannot infer missing columns `pd.IndexSlice[i, 21,]`. A colon has to be used `pd.IndexSlice[i, 21,:]` or pass an array instead of an `Index` object `[1,2,3]`

I don't know if this is intended.
