'Make edge in graph of parent domain to child subdomain.
GvGen nodes are created if not yet existing.
@param graph: gvgen.GvGen object
@param parent: parent DomainNode
@param child: child DomainNode'

def makeSubdomainEdge(self, graph, parent, child):

    if (not child.gvNode):
        child.gvNode = graph.newItem(child.subDomain)
        graph.propertyAppend(child.gvNode, 'shape', 'octagon')
    if (not parent.gvNode):
        parent.gvNode = graph.newItem((parent.subDomain or '<root>'))
        graph.propertyAppend(parent.gvNode, 'shape', 'octagon')
    graph.newLink(parent.gvNode, child.gvNode)
