Fix empty YNotebook

Author: hbcarlos

jupyter_ydoc/ynotebook.py

@@ -221,8 +221,8 @@ def get(self) -> Dict:
         return dict(
             cells=cells,
             metadata=meta.get("metadata", {}),
-            nbformat=int(meta.get("nbformat", 0)),
-            nbformat_minor=int(meta.get("nbformat_minor", 0)),
+            nbformat=int(meta.get("nbformat", NBFORMAT_MAJOR_VERSION)),
+            nbformat_minor=int(meta.get("nbformat_minor", NBFORMAT_MINOR_VERSION)),
         )
 
     def set(self, value: Dict) -> None:

pyproject.toml

@@ -31,7 +31,7 @@ test = [
     "pytest",
     "pytest-asyncio",
     "websockets >=10.0",
-    "ypy-websocket >=0.8.3,<0.9.0",
+    "ypy-websocket >=0.8.3,<0.13.0",
 ]
 docs = [
     "sphinx",