def uniquify(lst):
    """
    Make the elements of a list unique by inserting them into a dictionary.
    This must not change the order of the input lst.
    """
    dct = {}
    result = []
    for k in lst:
        if k not in dct:
            result.append(k)
        dct[k] = 1
    return result

    Make the elements of a list unique by inserting them into a dictionary.
    This must not change the order of the input lst.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/util.py