Fixed #30 : Add variable support in BNF concept definition

Fixed #31 : Add regex support in BNF Concept
Fixed #33 : Do not memorize object during restore

src/sheerkapickle/SheerkaUnpickler.py

@@ -1,7 +1,7 @@
 import json
 
 import core.utils
-from core.global_symbols import NotInit, NotFound, Removed
+from core.global_symbols import NotInit, NotFound, Removed, NoFirstToken
 from sheerkapickle import tags, utils, handlers
 
 
@@ -54,6 +54,8 @@ class SheerkaUnpickler:
             instance = NotFound
         elif obj[tags.CUSTOM] == Removed.value:
             instance = Removed
+        elif obj[tags.CUSTOM] == NoFirstToken.value:
+            instance = NoFirstToken
         else:
             raise KeyError(f"unknown  {obj[tags.CUSTOM]}")