Implemented a first and basic version of a Rete rule engine

tests/TestUsingFileBasedSheerka.py

@@ -1,4 +1,5 @@
 from conftest import SHEERKA_TEST_FOLDER
+from core.global_symbols import EVENT_ONTOLOGY_CREATED
 from core.sheerka.Sheerka import Sheerka
 from core.sheerka.SheerkaOntologyManager import SheerkaOntologyManager
 
@@ -10,19 +11,28 @@ class TestUsingFileBasedSheerka(BaseTest):
     context = None
     root_ontology_name = SheerkaOntologyManager.ROOT_ONTOLOGY_NAME
 
+    ontologies_created = set()
+
     def teardown_method(self, method):
         # to do after the test
         if TestUsingFileBasedSheerka.sheerka:
             while TestUsingFileBasedSheerka.sheerka.om.current_ontology().name != self.root_ontology_name:
-                ontology = TestUsingFileBasedSheerka.sheerka.pop_ontology().body.body
+                ontology = TestUsingFileBasedSheerka.sheerka.pop_ontology(self.context).body.body
                 ontology.cache_manager.sdp.test_only_destroy_refs()
 
+            # remove other created ontologies
+            for ontology in TestUsingFileBasedSheerka.ontologies_created:
+                TestUsingFileBasedSheerka.sheerka.om.current_sdp().test_only_destroy_refs(ontology)
+            TestUsingFileBasedSheerka.ontologies_created.clear()
+
     @staticmethod
     def new_sheerka_instance(cache_only):
         sheerka = Sheerka(cache_only=cache_only)
         sheerka.initialize(SHEERKA_TEST_FOLDER,
                            save_execution_context=False,
-                           enable_process_return_values=False)
+                           enable_process_return_values=False,
+                           enable_process_rules=False)
+        sheerka.subscribe(EVENT_ONTOLOGY_CREATED, lambda c, o: TestUsingFileBasedSheerka.ontologies_created.add(o))
         return sheerka
 
     def get_sheerka(self, **kwargs) -> Sheerka: