Describe the bug

When querying activity partitions and seeing what nodes under which partition is, it was discovered that the first partition in the set gets all the nodes and all the rest are empty.

To Reproduce

Steps to reproduce the behavior:

1. Create the following activity diagram
   
2. Open console and write

from gaphor.UML import uml
[f'{p.name}: {[n.name for n in p.node]}' for p in select(uml.ActivityPartition)]

3. See that the output is: ["Swimlane One: ['A1', 'A2']", 'New Swimlane: []']

Expected behavior

Expected output of the steps should be ["Swimlane One: ['A1']", "New Swimlane: ['A2']"]

OS

• Linux (Mint)
• macOS
• Windows

Version

Version of Gaphor: 2.23.2