def merge(dic, diff):
    """
    Merge mapping objects.

    :param dic: Original mapping object to update with `diff`
    :param diff: Diff mapping object
    :return: None but `dic` will be updated

    >>> dic = {}
    >>> merge(dic, {'a': 1})
    >>> assert 'a' in dic and dic['a'] == 1
    """
    dic.update(diff)
