Letter Tile Possibilities LeetCode solution in Python

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class Solution:
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    def numTilePossibilities(self, tiles: str) -> int:
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        n = len(tiles)
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        tiles = list(tiles)
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        s1 = set()
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        for i in range(1, n + 1):
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            s1.update(permutations(tiles, i))
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        return len(s1)