def to_list(var):
    """Checks if given value is a list, tries to convert, if it is not."""
    if var is None:
        return []
    if isinstance(var, str):
        var = var.split('\n')
    elif not isinstance(var, list):
        try:
            var = list(var)
        except TypeError:
            raise ValueError("{} cannot be converted to the list.".format(var))
    return var
Checks if given value is a list, tries to convert, if it is not.