how to remove the 3rd dimension for gray image in opencv

Question

I use Allied Vision camera to capture frame, and their Vimba API, but stuck in 3 channel grayscale image.

with Vimba.get_instance() as vimba:
            cams = vimba.get_all_cameras()
            with cams[0] as camera:
                recv_image = camera.get_frame()
                recv_image.convert_pixel_format(PixelFormat.Mono8)
                t1 = recv_image.as_opencv_image()
                #t1 has a dimension (xx,xx,1), I want to remove the last channel
                cv2image = cv2.cvtColor(t1, cv2.COLOR_BGR2GRAY)
                #not working as cv2.cvtcolor does not take (xx,xx,1) input

**update:**even Christoph shows a numpy way to convert 3-d to 2-d, but I found I could not use some OpenCV commands, how to convert it back to OpenCV image? anyway I temporarily use a very stupid way to serve the purpose, but I still want the neat way to do this

 recv_image.convert_pixel_format(PixelFormat.Mono8)
 cv2.imwrite('cv2image.jpg', recv_image.as_opencv_image())
 cv2image = cv2.imread('cv2image.jpg',0)

Update: finally I could use numpy to do this instead of saving image, thanks to christoph

frame.convert_pixel_format(PixelFormat.Mono8)
                        a = frame.as_opencv_image()
                        b = np.array(a)
                        cv2image = np.squeeze(b)