Naming a Company LeetCode solution in Python

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class Solution:
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    def distinctNames(self, ideas: List[str]) -> int:
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        names = defaultdict(set)
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        res = 0
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        # to store first letter as key and followed suffix as val
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        for i in ideas:
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            names[i[0]].add(i[1:])
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        # list of distinct first-letters available in ideas (may or may not contain all alphabets,depends upon elements in ideas)
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        arr = list(names.keys())
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        ans, n = 0, len(arr)
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        for i in range(n):
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            for j in range(i + 1, n):
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                # a,b => 2 distinct first letters
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                a, b = arr[i], arr[j]
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                # adding the number of distinct posssible suffixes and multiplying by 2 as the new word formed might be "newword1 newword2" or "newword2 newword1"
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                res += len(names[a] - names[b]) * len(names[b] - names[a]) * 2
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        return res