def _scroll(clicks, x=None, y=None):
    """Send the mouse vertical scroll event to Windows by calling the
    mouse_event() win32 function.

    Args:
      clicks (int): The amount of scrolling to do. A positive value is the mouse
      wheel moving forward (scrolling up), a negative value is backwards (down).
      x (int): The x position of the mouse event.
      y (int): The y position of the mouse event.

    Returns:
      None
    """
    startx, starty = _position()
    width, height = _size()

    if x is None:
        x = startx
    else:
        if x < 0:
            x = 0
        elif x >= width:
            x = width - 1
    if y is None:
        y = starty
    else:
        if y < 0:
            y = 0
        elif y >= height:
            y = height - 1

    try:
        _sendMouseEvent(MOUSEEVENTF_WHEEL, x, y, dwData=clicks)
    except (PermissionError, OSError): # TODO: We need to figure out how to prevent these errors, see https://github.com/asweigart/pyautogui/issues/60
            pass
Send the mouse vertical scroll event to Windows by calling the
    mouse_event() win32 function.

    Args:
      clicks (int): The amount of scrolling to do. A positive value is the mouse
      wheel moving forward (scrolling up), a negative value is backwards (down).
      x (int): The x position of the mouse event.
      y (int): The y position of the mouse event.

    Returns:
      None