First Day Where You Have Been in All the Rooms LeetCode solution in Python

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class Solution:
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    def firstDayBeenInAllRooms(self, nextVisit: List[int]) -> int:
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        n: int = len(nextVisit)
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        days: List[int] = n * [
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            0
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        ]  # days[i] is the number of days it takes to first reach room i
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        MOD = pow(10, 9) + 7
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        for i in range(0, n - 1):
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            # First we are already at room i. days[i] days has passed
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            days[i + 1] = days[i]
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            # lets go from room i to room i+1.
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            # When we first visit room i, we need to visit room i again (so room i is visited twice, which is an even number), then we can visit room i+1
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            # after we fist visit room i, the next day we will visit room (nextVisit[i]).
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            days[i + 1] = (days[i + 1] + 1) % MOD
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            # Then the problem becomes "how to go from room (nextVisit[i]) back to room i". The step is (days[i] - days[nextVisit[i]])
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            days[i + 1] = (days[i + 1] + days[i] - days[nextVisit[i]]) % MOD
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            # Then, in the next day we go from room i to i+1
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            days[i + 1] = (days[i + 1] + 1) % MOD
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        return days[n - 1]