def parent(children, parent, relative=True, absolute=False):
    assert isinstance(parent, DagNode), 'parent must be DagNode'
    if (not isinstance(children, (tuple, list))):
        children = [children]
    for child in children:
        assert isinstance(child, DagNode), 'child must be DagNode'
        parent.addChild(child)
def parent(children, parent, relative=True, absolute=False):
    assert isinstance(parent, DagNode), 'parent must be DagNode'
    if (not isinstance(children, (tuple, list))):
        children = [children]
    for child in children:
        assert isinstance(child, DagNode), 'child must be DagNode'
        parent.addChild(child)