Sort Characters by frequency

class Solution(object):
    def frequencySort(self, s):
        output=""
        dict={}
        for char in s: #making dictionary from character and characters frequency pair
            if char in dict:
                dict[char]+=1
            else:
                dict[char]=1
        
        sorted_dict=sorted(dict, key=dict.get, reverse=True) #sorting dict based on value
        for char in sorted_dict: #storing in output
            output+= char*dict[char]
        
        return output