def transform_to_dict(closest_list: list) -> dict:
    """
    Returns dict {(latitude, longitude): {film1, film2, ...}, ...} from
    closest_list [[film1, (latitude, longitude)], ...], where film1,
    film2 are titles of films, (latitude, longitude) is a coordinates of
    a place where those films were shoot.

    >>> transform_to_dict([["film1", (49, 24)]])
    {(49, 24): {'film1'}}
    """

    closest_dict = {}
    for film, coord in closest_list:
        if coord in closest_dict:
            closest_dict[coord].add(film)
        else:
            closest_dict[coord] = {film}
    return closest_dict