diff --git a/solutions/system_design/social_graph/social_graph_snippets.py b/solutions/system_design/social_graph/social_graph_snippets.py
index f0ea4c4b..d348a4d7 100644
--- a/solutions/system_design/social_graph/social_graph_snippets.py
+++ b/solutions/system_design/social_graph/social_graph_snippets.py
@@ -11,6 +11,7 @@ class State(Enum):
 class Graph(object):
 
     def bfs(self, source, dest):
+        """ Return True if there is a path from source to dest."""
         if source is None:
             return False
         queue = deque()