refactor(helpers): TPKTYPETREE init

Author: isHarryh

UnityPy/helpers/Tpk.py

@@ -8,18 +8,19 @@
 
 from .TypeTreeHelper import TypeTreeNode
 
-TPKTYPETREE: TpkTypeTreeBlob = None
-CLASSES_CACHE: Dict[Tuple[int, tuple], TypeTreeNode] = {}
-NODES_CACHE: Dict[TpkUnityClass, TypeTreeNode] = {}
-
 
-def init():
+def init_tpk_typetree():
     with open_binary("UnityPy.resources", "uncompressed.tpk") as f:
         data = f.read()
-
-    global TPKTYPETREE
     with BytesIO(data) as stream:
-        TPKTYPETREE = TpkFile(stream).GetDataBlob()
+        blob = TpkFile(stream).GetDataBlob()
+        assert isinstance(blob, TpkTypeTreeBlob)
+        return blob
+
+
+TPKTYPETREE: TpkTypeTreeBlob = init_tpk_typetree()
+CLASSES_CACHE: Dict[Tuple[int, tuple], TypeTreeNode] = {}
+NODES_CACHE: Dict[TpkUnityClass, TypeTreeNode] = {}
 
 
 def get_typetree_node(class_id: int, version: tuple):
@@ -535,6 +536,3 @@ def get_item_for_version(
     if ret:
         return ret
     raise ValueError("Could not find exact version")
-
-
-init()