Add script source.

combo/utils/graph.py

@@ -88,6 +88,7 @@ def _dfs(graph, start, end):
 
 
 def restore_collapse_edges(tree_tokens):
+    # https://gist.github.com/hankcs/776e7d95c19e5ff5da8469fe4e9ab050
     empty_tokens = []
     for token in tree_tokens:
         deps = token["deps"].split("|")