TST: minor simplification of test code

unittests/test_sync_graph.py

@@ -185,12 +185,10 @@ def test_merge_into_trivial(simple_adapter):
     b = db.Record(id=101).add_parent("RT1")
 
     st = SyncGraph([a, b], simple_adapter)
-    se_a = st.nodes[0]
-    se_b = st.nodes[1]
-    se_c = st.nodes[2]
-    assert se_a.name is 'a'
-    assert se_b.id is 101
-    assert se_c.name is 'c'
+    se_a, se_b, se_c = st.nodes
+    assert se_a.name == 'a'
+    assert se_b.id == 101
+    assert se_c.name == 'c'
 
     # CHECK REFERENCE MAP (before merge):
     # c is referenced by a