put code into functions

skimage/graph/rag.py

@@ -164,8 +164,13 @@ class RAG(nx.Graph):
         """
         return self.max_id + 1
 
-    def _add_node(self, u):
-        super(RAG, self).add_node(u)
+    def _add_node_silent(self, n):
+        """Add node `n` without updating the maximum node id.
+
+        This is a convenience method used internally.
+
+        .. seealso:: :func:`networkx.Graph.add_node`."""
+        super(RAG, self).add_node(n)
 
 
 def _add_edge_filter(values, graph):