First Unique Number Python Solution with Tests

lcpy gen -n 1429   # by problem number
lcpy gen -s first_unique_number   # by problem name

Input
["FirstUnique", "showFirstUnique", "add", "showFirstUnique", "add", "showFirstUnique", "add", "showFirstUnique"]
[[[2, 3, 5]], [], [5], [], [2], [], [3], []]
Output
[null, 2, null, 2, null, 3, null, -1]

Input
["FirstUnique", "showFirstUnique", "add", "add", "add", "add", "add", "showFirstUnique"]
[[[7, 7, 7, 7, 7, 7]], [], [7], [3], [3], [7], [17], []]
Output
[null, -1, null, null, null, null, null, 17]

Input
["FirstUnique", "showFirstUnique", "add", "showFirstUnique"]
[[[809]], [], [809], []]
Output
[null, 809, null, -1]

from collections import Counter, deque


class FirstUnique:
    # Time: __init__ O(n), show_first_unique amortized O(1), add O(1)
    # Space: O(n)
    def __init__(self, nums: list[int]) -> None:
        self.counts: Counter[int] = Counter(nums)
        self.queue: deque[int] = deque(nums)

    def show_first_unique(self) -> int:
        while self.queue and self.counts[self.queue[0]] != 1:
            self.queue.popleft()
        return self.queue[0] if self.queue else -1

    def add(self, value: int) -> None:
        self.counts[value] += 1
        self.queue.append(value)