¬ just serendipity 🍀 (not just serendipity)

from collections import defaultdict
from collections.abc import Hashable

def is_hashable(obj) -> bool:
    return isinstance(obj, Hashable)

class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        seen = defaultdict(list)

        for s in strs:
            cs = ''.join(sorted(s)) # canonical
            seen[cs].append(s)

        return list(seen.values())