Always return ModelRepresentative object

If there is no user-provided representative
model, auto-generate a ModelRepresentative
object that wraps the selected model. Relates #174.

Author: benmwebb

ihm/__init__.py

@@ -271,7 +271,9 @@ def _all_models(self):
     def get_representative_model(self):
         """Get a single :class:`~model.ModelRepresentative` that best
            represents the entire System. If no representatives have been
-           provided, the :class:`~model.Model` containing the most chains
+           provided, an auto-generated :class:`~model.ModelRepresentative`
+           (with ``selection_criteria`` of ``auto``), wrapping the
+           :class:`~model.Model` containing the most chains,
            is returned instead."""
         repmodel = None
         repmodel_chains = -1
@@ -287,7 +289,10 @@ def get_representative_model(self):
         if repmodel is None:
             raise ValueError("No models")
         else:
-            return repmodel
+            import ihm.model
+            m = ihm.model.ModelRepresentative(repmodel, 'medoid')
+            m._selection_criteria = 'auto'
+            return m
 
     def update_locations_in_repositories(self, repos):
         """Update all :class:`~ihm.location.Location` objects in the system

test/test_main.py

@@ -1434,8 +1434,10 @@ def test_get_representative_model(self):
         s.state_groups.append(ihm.model.StateGroup([state]))
 
         # m2 contains two chains to m1's one, so it should be selected
-        # by default
-        self.assertIs(s.get_representative_model(), m2)
+        # by default (as an auto-generated model)
+        r = s.get_representative_model()
+        self.assertIs(r.model, m2)
+        self.assertEqual(r.selection_criteria, 'auto')
 
         # If we explicitly denote m1 as the representative, it should
         # be returned instead