Added block walker implementations + tests

tests/abstract_test.py

@@ -1,3 +1,4 @@
+import logging
 import pathlib
 import unittest
 
@@ -6,6 +7,7 @@ class AbstractBlendFileTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         cls.blendfiles = pathlib.Path(__file__).with_name('blendfiles')
+        logging.basicConfig(level=logging.INFO)
 
     def setUp(self):
         self.bf = None