Each letter in the magazine string can only be used once in your ransom note.

Note:You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> falsecanConstruct("aa", "ab") -> falsecanConstruct("aa", "aab") -> true
class Solution(object):    def canConstruct(self, ransomNote, magazine):        """        :type ransomNote: str        :type magazine: str        :rtype: bool        """        import collections        return not collections.Counter(ransomNote) - collections.Counter(magazine)