def dict_append_to_value_lists(dict_appendee, dict_new):
    """
    Appends values from dict_new to list of values with same key in dict_appendee
    Args:
        dict_appendee: dict with value lists (as created by dict_values_to_lists function
        dict_new: dict with new values that need to be appended to dict_appendee

    Returns:
        dict with appended values
    """
    if dict_new is None:
        return None

    for key in dict_new.keys():
        if type(dict_appendee[key]) != list:
            raise TypeError("Dict value is not a list")

        dict_appendee[key] += [dict_new[key]]

    return dict_appendee