Create pydot Nodes.

def _get_go2pydotnode(self):
        """Create pydot Nodes."""
        go2node = {}
        go2obj = self.gosubdag.go2obj
        get_node = self.pydotnodego.get_node
        for goid in self.get_goids_plt():
            goobj = go2obj[goid]
            node = get_node(goid, goobj)
            go2node[goid] = node
            if goid != goobj.id: # goid is an alias for goobj
                go2node[goobj.id] = node
        return go2node