improve 2-3 codebase compatibility

tests/document/__init__.py

@@ -1,13 +1,13 @@
 import unittest
 
-from class_methods import *
-from delta import *
-from dynamic import *
-from indexes import *
-from inheritance import *
-from instance import *
-from json_serialisation import *
-from validation import *
+from .class_methods import *
+from .delta import *
+from .dynamic import *
+from .indexes import *
+from .inheritance import *
+from .instance import *
+from .json_serialisation import *
+from .validation import *
 
 if __name__ == '__main__':
     unittest.main()