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_utils.py

@@ -469,3 +469,28 @@ def test_tokens_are_matching_when_eof_differs():
     tokens2 = Tokenizer(expression2, yield_eof=False)
 
     assert core.utils.tokens_are_matching(tokens1, tokens2)
+
+
+def test_sheerka_hasattr_get_attr():
+    class A:
+        def __init__(self, property_value):
+            self.property_value = property_value
+
+        def as_bag(self):
+            return {"prop": self.property_value}
+
+    # test object with bag
+    a = A("foo")
+    assert core.utils.sheerka_hasattr(a, "prop")
+    assert core.utils.sheerka_getattr(a, "prop") == "foo"
+    assert not core.utils.sheerka_hasattr(a, "property_value")
+    with pytest.raises(AttributeError):
+        core.utils.sheerka_getattr(a, "property_value")
+
+    # test for concept
+    concept = Concept("foo").def_var("a", "value").auto_init()
+    assert core.utils.sheerka_hasattr(concept, "a")
+    assert core.utils.sheerka_getattr(concept, "a") == "value"
+    assert not core.utils.sheerka_hasattr(concept, "b")
+    with pytest.raises(AttributeError):
+        core.utils.sheerka_getattr(concept, "b")