Create pydot Nodes.

def _get_go2pydotnode(self):
        """Create pydot Nodes."""
        go2node = {}
        for goid, goobj in self.godag.go2obj.items():
            txt = self._get_node_text(goid, goobj)
            fillcolor = self.goid2color.get(goid, "white")
            node = self.pydot.Node(
                txt,
                shape="box",
                style="rounded, filled",
                fillcolor=fillcolor,
                color="mediumseagreen")
            go2node[goid] = node
        return go2node