Python: remove duplicates from a list/sequence while retaining the original order

sequence.py

from typing import List, Sequence
 
 
def unique_with_order(sequence: Sequence) -> List:
    """
    Returns the original sequence as a list with duplicates removed
    but, unlike simply using set, the original order is retained.
    """
    seen = set()
    return [x for x in sequence if not (x in seen or seen.add(x))]

test_sequence.py

import pytest
 
from your_path import unique_with_order
 
 
@pytest.mark.parametrize('input_sequence,expected', [
    ((1, 3, 2, 2, 1), [1, 3, 2]),
    (['a', 'z', 't', 't', 'tt', 'e'], ['a', 'z', 't', 'tt', 'e'])
])
def test_unique_with_order(input_sequence, expected):
    assert unique_with_order(input_sequence) == expected