def remove_empty_cells(obj: list[str]):
    """ remove empty cells

    Used to remove [], [""], and "" from nested lists.

    Parameters
    ----------
    obj: Any

    Returns
    -------
    output: Any

    """
    if not isinstance(obj, list):
        return obj
    if obj == []:
        return None

    out = []
    for ob in obj:
        if isinstance(ob, list):
            result = remove_empty_cells(ob)
            if result is not None:
                out.append(result)

        elif isinstance(ob, str) and ob == "":
            continue

        else:
            out.append(ob)

    # nothing was added to default list
    if out == []:
        return None

    return out