All is in the title : May a column from a python pandas dataframe be a list or ensemble or tuple or ... ?

```
 import pandas as pd

    lnks = [ ( 'a' , 'b') , ( 'b' , 'c') , ( 'c' , 'a' ) , ('b' , 'd' ) , ( 'd' , 'a' ) ]

    lbls = [ 'x' , 'y']

    df = pd.DataFrame.from_records( lnks , columns = lbls )

```

Trying to build a new column z of type ensemble from columns x and y row values :

```
df[ 'z' ] =  { df[ 'x' ] , df[ 'y' ] }

```

I get the following error code :

TypeError: 'Series' objects are mutable, thus they cannot be hash

I would like to obtain a dataframe containing :

```
x y z

'a' 'b' { 'a  , 'b' }
'b' 'c' { 'b' , 'c' }
'c' 'a' { 'c' , 'a' }
...

```

Thanks for your help.