属性错误：图像实例没有属性＆＃39; detectFaces＆＃39;

Question

from imgproc import *

cam = Camera(160, 120)
view = Viewer(cam.width, cam.height, "Face detection")

while True:
    image = cam.grabImage()

    faces = image.detectFaces()

    for face in faces:
        # extract the x, y, width and height from the tuple
        x, y, width, height = face

        # use this information to draw an orange rectangle around the face
        image.drawRect(x, y, width, height, 128, 0, 255)

    view.displayImage(image)