Merge pull request #120 from JoOkuma/wrong-frame-attribute

Improving error message when wrong frame is provided

motile/track_graph.py

@@ -120,13 +120,22 @@ def add_from_nx_graph(self, nx_graph: networkx.DiGraph) -> None:
                 or edges do already exist, the values set in the given ``nx_graph``
                 will be updating the previously set values.
         """
+        nodes_count = 0
         # add all regular nodes (all but ones representing hyperedges)
         for node, data in nx_graph.nodes.items():
             if self.frame_attribute in data:
                 if node not in self.nodes:
                     self.nodes[node] = data
                 else:
                     self.nodes[node] |= data
+                nodes_count += 1
+
+        # graph without nodes, it's very likely this was not intentional
+        if nodes_count == 0:
+            raise KeyError(
+                f"No nodes with `frame_attribute` '{self.frame_attribute}' found in "
+                "the `nx_graph`.\nIt's likely the wrong `frame_attribute` was set."
+            )
 
         # add all edges and hyperedges
         for (u, v), data in nx_graph.edges.items():