Performs a mouse drag (mouse movement while a button is held down) to a
    point on the screen, relative to its current position.

    The x and y parameters detail where the mouse event happens. If None, the
    current mouse position is used. If a float value, it is rounded down. If
    outside the boundaries of the screen, the event happens at edge of the
    screen.

    Args:
      x (int, float, None, tuple, optional): How far left (for negative values) or
        right (for positive values) to move the cursor. 0 by default. If tuple, this is used for xOffset and yOffset.
      y (int, float, None, optional): How far up (for negative values) or
        down (for positive values) to move the cursor. 0 by default.
      duration (float, optional): The amount of time it takes to move the mouse
        cursor to the new xy coordinates. If 0, then the mouse cursor is moved
        instantaneously. 0.0 by default.
      tween (func, optional): The tweening function used if the duration is not
        0. A linear tween is used by default. See the tweens.py file for
        details.
      button (str, int, optional): The mouse button clicked. Must be one of
        'left', 'middle', 'right' (or 1, 2, or 3) respectively. 'left' by
        default.
      mouseDownUp (True, False): When true, the mouseUp/Down actions are not perfomed.
        Which allows dragging over multiple (small) actions. 'True' by default.

    Returns:
      None

def dragRel(xOffset=0, yOffset=0, duration=0.0, tween=linear, button='left', pause=None, _pause=True, mouseDownUp=True):
    """Performs a mouse drag (mouse movement while a button is held down) to a
    point on the screen, relative to its current position.

    The x and y parameters detail where the mouse event happens. If None, the
    current mouse position is used. If a float value, it is rounded down. If
    outside the boundaries of the screen, the event happens at edge of the
    screen.

    Args:
      x (int, float, None, tuple, optional): How far left (for negative values) or
        right (for positive values) to move the cursor. 0 by default. If tuple, this is used for xOffset and yOffset.
      y (int, float, None, optional): How far up (for negative values) or
        down (for positive values) to move the cursor. 0 by default.
      duration (float, optional): The amount of time it takes to move the mouse
        cursor to the new xy coordinates. If 0, then the mouse cursor is moved
        instantaneously. 0.0 by default.
      tween (func, optional): The tweening function used if the duration is not
        0. A linear tween is used by default. See the tweens.py file for
        details.
      button (str, int, optional): The mouse button clicked. Must be one of
        'left', 'middle', 'right' (or 1, 2, or 3) respectively. 'left' by
        default.
      mouseDownUp (True, False): When true, the mouseUp/Down actions are not perfomed.
        Which allows dragging over multiple (small) actions. 'True' by default.

    Returns:
      None
    """
    if xOffset is None:
        xOffset = 0
    if yOffset is None:
        yOffset = 0

    if type(xOffset) in (tuple, list):
        xOffset, yOffset = xOffset[0], xOffset[1]

    if xOffset == 0 and yOffset == 0:
        return # no-op case

    _failSafeCheck()

    mousex, mousey = platformModule._position()
    if mouseDownUp:
        mouseDown(button=button, _pause=False)
    _mouseMoveDrag('drag', mousex, mousey, xOffset, yOffset, duration, tween, button)
    if mouseDownUp:
        mouseUp(button=button, _pause=False)

    _autoPause(pause, _pause)