group anagrams

def sort_string(self,strs):
        a = [i for i in strs]
        a.sort()
        return ''.join(a)
    
    def groupAnagrams(self,strs):
        sol_set,solution = dict(),[]
        for x in strs:
            if self.sort_string(x) in sol_set.keys():
                sol_set[self.sort_string(x)].append(x)
            else:
                sol_set[self.sort_string(x)] = [x]
        for x in sol_set.values():
            solution.append(x)
        return solution