def typedef_handle(self, tokens):
        """Process Python 3 type annotations."""
        if len(tokens) == 1:  # return typedef
            if self.target.startswith("3"):
                return " -> " + self.wrap_typedef(tokens[0]) + ":"
            else:
                return ":\n" + self.wrap_comment(" type: (...) -> " + tokens[0])
        else:  # argument typedef
            if len(tokens) == 3:
                varname, typedef, comma = tokens
                default = ""
            elif len(tokens) == 4:
                varname, typedef, default, comma = tokens
            else:
                raise CoconutInternalException("invalid type annotation tokens", tokens)
            if self.target.startswith("3"):
                return varname + ": " + self.wrap_typedef(typedef) + default + comma
            else:
                return varname + default + comma + self.wrap_passthrough(self.wrap_comment(" type: " + typedef) + "\n" + " " * self.tabideal)
Process Python 3 type annotations.