code: def pinch(self, scale, velocity):
          
          data = {'scale': scale, 'velocity': velocity}
          return self._wda_req('post', '/pinch', data)
docs: 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