renamed node_graph() to nodeGraph() to be compatible with the naming convention

pykat/finesse.py

@@ -2089,9 +2089,9 @@ class kat(object):
         
         return out
 
-    def node_graph(self, output):
+    def nodeGraph(self, output):
         """
-        node_graph(output)
+        nodeGraph(output)
 
         Generate node visualisation of pykat node network using the
         pygraphviz package. The generated graphics is saved in output, where the