Walk tree of nodes to root

    :param reducibleChildren: nodes which are part of tree
    :param nodeFromTree: node where to start the search

def searchRootOfTree(reducibleChildren: Set[LNode], nodeFromTree: LNode):
    """
    Walk tree of nodes to root

    :param reducibleChildren: nodes which are part of tree
    :param nodeFromTree: node where to start the search
    """

    while True:
        out_e = nodeFromTree.east[0].outgoingEdges
        # node has no successors
        if not out_e:
            return nodeFromTree

        nextNode = out_e[0].dsts[0].parentNode
        if nextNode in reducibleChildren:
            # can reduce node, walk the tree to root
            nodeFromTree = nextNode
        else:
            # can not reduce, return last root of tree
            return nodeFromTree