Fix sampling when there is no node with id 0.

lynxkite-graph-analytics/src/lynxkite_plugins/graph_analytics/lynxkite_ops.py

@@ -253,7 +253,7 @@ def organize_bundle(bundle: Bundle, *, code: ops.LongStr):
 def sample_graph(graph: nx.Graph, *, nodes: int = 100):
     """Takes a (preferably connected) subgraph."""
     sample = set()
-    to_expand = deque([0])
+    to_expand = deque([next(graph.nodes.keys().__iter__())])
     while to_expand and len(sample) < nodes:
         node = to_expand.pop()
         for n in graph.neighbors(node):