def to_list(obj):
    """List Converter

    Takes any object and converts it to a `list`.
    If the object is already a `list` it is just returned,
    If the object is None an empty `list` is returned,
    Else a `list` is created with the object as it's first element.

    Args:
        obj (any object): the object to be converted

    Returns:
        A list containing the given object
    """
    if isinstance(obj, list):
        return obj
    elif isinstance(obj, tuple):
        return list(obj)
    elif obj is None:
        return []
    else:
        return [obj, ]