issue #8854: Class hierarchy diagram is not correct, if inherited fro…

…m Python built-in class ABC

src/dotnode.cpp

@@ -806,19 +806,18 @@ void DotNode::renumberNodes(int &number)
   level++;
 #endif
   m_number = number++;
+  markRenumbered();
   for (const auto &cn : m_children)
   {
     if (!cn->isRenumbered())
     {
-      cn->markRenumbered();
       cn->renumberNodes(number);
     }
   }
   for (const auto &pn : m_parents)
   {
     if (!pn->isRenumbered())
     {
-      pn->markRenumbered();
       pn->renumberNodes(number);
     }
   }