def pinch(self, scale, velocity):
        """
        Args:
            scale (float): scale must > 0
            velocity (float): velocity must be less than zero when scale is less than 1
        
        Example:
            pinchIn  -> scale:0.5, velocity: -1
            pinchOut -> scale:2.0, velocity: 1
        """
        data = {'scale': scale, 'velocity': velocity}
        return self._wda_req('post', '/pinch', data)