Remove parameter from stamp method.

setup.py

@@ -10,7 +10,7 @@ def contents(*filenames):
 setup(
     name = "yangson",
     packages = ["yangson"],
-    version = "0.1.38",
+    version = "0.1.39",
     description = "Library for working with YANG schemas and data",
     author = "Ladislav Lhotka",
     author_email = "lhotka@nic.cz",

yangson/instance.py

@@ -21,7 +21,7 @@ class StructuredValue:
         """
         self.timestamp = ts
 
-    def stamp(self, ts: datetime = None) -> None:
+    def stamp(self) -> None:
         """Update the receiver's timestamp to current time."""
         self.timestamp = datetime.now()