Fix typing of Arguments.args (#1283)

Author: DanielNoord

ChangeLog

@@ -18,6 +18,8 @@ Release date: TBA
 
   Closes #1260
 
+* Fix typing and update explanation for ``Arguments.args`` being ``None``.
+
 
 What's New in astroid 2.9.0?
 ============================

astroid/nodes/node_classes.py

@@ -858,8 +858,13 @@ def __init__(
         self.kwarg: Optional[str] = kwarg  # can be None
         """The name of the variable length keyword arguments."""
 
-        self.args: typing.List[AssignName]
-        """The names of the required arguments."""
+        self.args: typing.Optional[typing.List[AssignName]]
+        """The names of the required arguments.
+
+        Can be None if the assosciated function does not have a retrievable
+        signature and the arguments are therefore unknown.
+        This happens with builtin functions implemented in C.
+        """
 
         self.defaults: typing.List[NodeNG]
         """The default values for arguments that can be passed positionally."""