def pinch(in_or_out='in', center=None, percent=0.5):
    """
    Perform the pinch action on the device screen

    :param in_or_out: pinch in or pinch out, enum in ["in", "out"]
    :param center: center of pinch action, default as None which is the center of the screen
    :param percent: percentage of the screen of pinch action, default is 0.5
    :return: None
    :platforms: Android
    :Example:

        Pinch in the center of the screen with two fingers::

        >>> pinch()

        Take (100,100) as the center and slide out with two fingers::

        >>> pinch('out', center=(100, 100))
    """
    try_log_screen()
    G.DEVICE.pinch(in_or_out=in_or_out, center=center, percent=percent)
    delay_after_operation()

    Perform the pinch action on the device screen

    :param in_or_out: pinch in or pinch out, enum in ["in", "out"]
    :param center: center of pinch action, default as None which is the center of the screen
    :param percent: percentage of the screen of pinch action, default is 0.5
    :return: None
    :platforms: Android
    :Example:

        Pinch in the center of the screen with two fingers::

        >>> pinch()

        Take (100,100) as the center and slide out with two fingers::

        >>> pinch('out', center=(100, 100))
    
airtest/core/api.py