TST: add test for filter function of Container

unittests/test_container.py

@@ -199,3 +199,12 @@ def test_container_slicing():
 
     with pytest.raises(TypeError):
         cont[[0, 2, 3]]
+
+def test_container_filter():
+    # this is a very rudimentary test since filter is based on _filter_entity_list which is tested
+    # separately
+    cont = db.Container()
+    cont.extend([db.Record(name=f"TestRec{ii+1}") for ii in range(5)])
+    recs = cont.filter(name="TestRec2")
+    assert len(recs)==1
+    recs[0].name =="TestRec2"