def _set_form(self, name: str, value: MultiDict[str, t.Any]) -> None:
        """Common behavior for setting the :attr:`form` and
        :attr:`files` properties.

        :param name: Name of the internal cached attribute.
        :param value: Value to assign to the attribute.
        """
        self._input_stream = None
        setattr(self, name, value)
Common behavior for setting the :attr:`form` and
        :attr:`files` properties.

        :param name: Name of the internal cached attribute.
        :param value: Value to assign to the attribute.
        
src/werkzeug/test.py