Fixed #68: Implement SheerkaQL

Fixed #70: SheerkaFilterManager : Pipe functions
Fixed #71: SheerkaFilterManager : filter_objects
Fixed #75: SheerkaMemory: Enhance memory() to use the filtering capabilities
Fixed #76: SheerkaEvaluateConcept: Concepts that modify the state of the system must not be evaluated during question

tests/core/test_SheerkaMemory.py

@@ -87,7 +87,9 @@ class TestSheerkaMemory(TestUsingMemoryBasedSheerka):
         foo = Concept("foo")
         sheerka.add_to_memory(context, "a", foo)
 
-        assert sheerka.om.copy(SheerkaMemory.OBJECTS_ENTRY) == {"a": MemoryObject(context.event.get_digest(), foo)}
+        assert sheerka.om.copy(SheerkaMemory.OBJECTS_ENTRY) == {"a": MemoryObject(context.event.get_digest(),
+                                                                                  context.event.date.timestamp(),
+                                                                                  foo)}
         assert id(sheerka.get_from_memory(context, "a").obj) == id(foo)
 
     def test_i_can_use_memory_with_a_string(self):
@@ -106,6 +108,44 @@ class TestSheerkaMemory(TestUsingMemoryBasedSheerka):
 
         assert sheerka.memory(context, Concept("foo")) == foo
 
+    def test_i_can_use_memory_with_a_query(self):
+        sheerka, context, foo, bar = self.init_concepts("foo", "bar")
+
+        sheerka.add_to_memory(context, "x", foo)
+        sheerka.add_to_memory(context, "y", bar)
+
+        assert sheerka.memory(context, "self.name == 'foo'") == foo
+
+    def test_i_retrieve_the_last_entry_when_requesting_memory_with_a_query(self):
+        sheerka, context, foo, bar, foo2 = self.init_concepts("foo", "bar", Concept("foo", body="2"))
+
+        sheerka.add_to_memory(context, "x", foo)
+        sheerka.add_to_memory(context, "y", bar)
+
+        context2 = self.get_context(sheerka)  # timestamp is newer
+        sheerka.add_to_memory(context2, "z", foo2)
+
+        assert sheerka.memory(context, "self.name == 'foo'") == foo2
+
+    def test_i_can_look_in_the_previous_objects_when_using_query_to_request_the_memory(self):
+        sheerka, context, foo, bar, baz = self.init_concepts("foo", "bar", "baz")
+
+        sheerka.add_to_memory(context, "x", foo)
+        sheerka.add_to_memory(context, "y", bar)
+        sheerka.add_to_memory(context, "z", baz)
+
+        # another layer
+        sheerka.add_to_memory(context, "x", bar)
+        sheerka.add_to_memory(context, "y", baz)
+
+        # another layer
+        sheerka.add_to_memory(context, "x", baz)
+
+        # so under x there is [foo] -> [bar] -> [baz]
+        # so under y there is [bar] -> [baz]
+        # so under z there is [baz]
+        assert sheerka.memory(context, "self.name == 'foo'") == foo
+
     def test_concept_not_found_is_return_when_not_found(self):
         sheerka, context = self.init_test().unpack()