Find Words That Can Be Formed by Characters

Problem Statement:

You are given an array of strings words and a string chars.
A string is good if it can be formed by characters from chars (each character can only be used once).
Return the sum of lengths of all good strings in words.

Example 1:
Input: words = ["cat","bt","hat","tree"], chars = "atach"
Output: 6
Explanation: 
The strings that can be formed are "cat" and "hat" so the answer is 3 + 3 = 6.

Example 2:
Input: words = ["hello","world","leetcode"], chars = "welldonehoneyr"
Output: 10
Explanation: 
The strings that can be formed are "hello" and "world" so the answer is 5 + 5 = 10.




Solution:
class Solution:
    def countCharacters(self, words: List[str], chars: str) -> int:
        if not chars:
            return 0
        ans=0
        for word in words:
            original=collections.Counter(chars)
            flag=True
            for letter in word:
                if letter in original:
                    flag=True
                    original[letter]-=1
                    if original[letter]==0:
                        del original[letter]
                else:
                    flag=False
                    break
            if flag:
                ans+=len(word)
        return ans