Minimum Deletions to Make Character Frequencies Unique LeetCode solution in Python

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class Solution:
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    def minDeletions(self, s: str) -> int:
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        # Get the frequency of each character sorted in reverse order
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        frequencies = sorted(Counter(s).values(), reverse=True)
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        total_deletions = 0
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        next_unused_freq = len(s)
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        for freq in frequencies:
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            # It is impossible for the frequency to be higher
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            next_unused_freq = min(next_unused_freq, freq)
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            total_deletions += freq - next_unused_freq
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            # We cannot have another character with this frequency,
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            # so decrement next_unused_freq
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            if next_unused_freq > 0:
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                next_unused_freq -= 1
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        return total_deletions