sage: SetPartition([["1", 2]])
...
/home/martin/sage-develop/local/lib/python3.7/site-packages/sage/combinat/set_partition.py in __init__(self, parent, s, check)
    567         """
    568         self._latex_options = {}
--> 569         ClonableArray.__init__(self, parent, sorted(map(frozenset, s), key=min), check=check)
    570 
    571     def check(self):
...
TypeError: unsupported operand parent(s) for >: 'Integer Ring' and '<class 'str'>'