from typing import Iterable
from typing import Sequence


def get_unique_list_in_order(list_of_lists: Iterable[Sequence]):
    """Gets unique items from a list of lists, in the order of the appearance

    Args:
        list_of_lists: list of lists

    Returns: list of unique items in order of appearance

    """
    output = []
    seen = set()
    for ls in list_of_lists:
        for elem in ls:
            if elem not in seen:
                output.append(elem)
                seen.add(elem)
    return output