[None][fix] the api_stability unify default values of None and inspect._empty (NVIDIA#8496)

Signed-off-by: Yan Chunwei <328693+Superjomn@users.noreply.github.com>

Author: Superjomn

tests/unittest/api_stability/api_stability_core.py

@@ -79,6 +79,11 @@ class ParamSnapshot:
     default: Any = None
     status: Optional[str] = None
 
+    def __post_init__(self):
+        # Unify default value of None and inspect._empty
+        if self.default is inspect._empty:
+            self.default = None
+
     @classmethod
     def from_inspect(cls, param: inspect.Parameter):
         return cls(param.annotation, param.default)