LC 0049 [M] Group Anagrams

class Solution:
    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
        sorted_to_words = defaultdict(list)
        for x in strs:
            key = tuple(sorted(x)) # tuple is hashable, but list is not
            sorted_to_words[key].append(x)
        return sorted_to_words.values()