Added debugging print statement

holoviews/element/sankey.py

@@ -162,15 +162,18 @@ def computeNodeDepths(self, graph):
         """
         nodes = graph['nodes']
         depth = 0
+        import inspect
         while nodes:
             next_nodes = []
+            print('>>>')
             for node in nodes:
                 node['depth'] = depth
                 for link in node['sourceLinks']:
+                    print(depth, len(inspect.stack()))
                     if link['target'] not in next_nodes:
                         next_nodes.append(link['target'])
             nodes = next_nodes
-            depth +=1
+            depth += 1
             if depth > 10000:
                 raise RecursionError('Sankey diagrams only support acyclic graphs.')