style: format source code using Ruff

tests/utils/ast_node.py

@@ -15,12 +15,11 @@
 from typing import Union
 import ast
 
-__all__ = [
-    'ast_node'
-]
+__all__ = ['ast_node']
+
 
 def ast_node(statement: str) -> Union[ast.stmt, None]:
-    '''
+    """
     Returns an AST node from the statement.
 
     :param statement: The statement.
@@ -28,7 +27,7 @@ def ast_node(statement: str) -> Union[ast.stmt, None]:
 
     :return: The node.
     :rtype: Union[ast.stmt, None]
-    '''
+    """
 
     body = ast.parse(statement).body
     if not body: