Update parser.py

parser.py

@@ -90,7 +90,7 @@ class Parser:
         self.match(func_name)
         self.match("OPEN_PAREN")
         arg = None
-        if self.current()[0] not in ("CLOSE_PAREN",):
+        if self.current()[0] != "CLOSE_PAREN":
             arg = self.expression()
         self.match("CLOSE_PAREN")
         self.match("SEMICOLON")