trying to fix build error - 1

graphs/directed_and_undirected_weighted_graph.py

@@ -185,6 +185,11 @@ class DirectedGraph:
         >>> g.add_pair(2, 3)
         >>> g.topological_sort()
         [1, 2, 3]
+        >>> g.add_pair(3, 1)  # Introducing a cycle
+        >>> g.topological_sort()
+        Traceback (most recent call last):
+            ...
+        ValueError: Graph has cycles, cannot perform topological sort.
         """
         stack = []
         visited = []
@@ -223,6 +228,9 @@ class DirectedGraph:
         >>> g.add_pair(2, 1)
         >>> g.cycle_nodes()
         [1, 2]
+        >>> g.add_pair(2, 3)
+        >>> g.cycle_nodes()  # No cycles now
+        []
         """
         stack = []
         visited = []
@@ -277,6 +285,12 @@ class DirectedGraph:
         >>> g.add_pair(2, 1)
         >>> g.has_cycle()
         True
+        >>> g.add_pair(2, 3)
+        >>> g.has_cycle()
+        True  # Still has a cycle
+        >>> g.remove_pair(1, 2)  # Now no cycle
+        >>> g.has_cycle()
+        False
         """
         stack = []
         visited = []