def set_elem(elem_ref, elem):
    """
    Sets element referenced by the elem_ref. Returns the elem.

    :param elem_ref:
    :param elem:
    :return:
    """
    if elem_ref is None or elem_ref == elem or not is_elem_ref(elem_ref):
        return elem

    elif elem_ref[0] == ElemRefObj:
        setattr(elem_ref[1], elem_ref[2], elem)
        return elem

    elif elem_ref[0] == ElemRefArr:
        elem_ref[1][elem_ref[2]] = elem
        return elem