def add_many_to_dict_val_list(dict_obj, key, val_list):
    """Adds the given value list to the list mapped by the given key.
    If the key is missing from the dict, the given mapping is added.

    Example
    -------
    >>> dict_obj = {'a': [1, 2]}
    >>> add_many_to_dict_val_list(dict_obj, 'a', [2, 3])
    >>> print(dict_obj['a'])
    [1, 2, 2, 3]
    >>> add_many_to_dict_val_list(dict_obj, 'b', [2, 3])
    >>> print(dict_obj['b'])
    [2, 3]
    """
    try:
        dict_obj[key].extend(val_list)
    except KeyError:
        dict_obj[key] = list(val_list)