ros cv2_to_imgmsg的问题

很短一段代码，看着也没问题，有没有帮我试试哪里错了

#! /usr/bin/env python
import rospy
import cv2
from cv_bridge import CvBridge as bridge
from sensor_msgs.msg import Image
import numpy as np

if __name__ == "__main__":

    rospy.init_node("pubtest")

    pub = rospy.Publisher("/hikrobot_camera/rgb",Image)

    cv_image=cv2.imread('/home/wzc/yolov5_pytorch_ros/src/yolov5/scripts/data/images/bus.jpg')
    im2 = np.array(cv_image)
    im=bridge.cv2_to_imgmsg(im2, "bgr8")

Traceback (most recent call last):
  File "/home/wzc/yolov5_pytorch_ros/src/yolov5/scripts/pubtest.py", line 16, in <module>
    im=bridge.cv2_to_imgmsg(im2, "bgr8")
  File "/opt/ros/melodic/lib/python2.7/dist-packages/cv_bridge/core.py", line 246, in cv2_to_imgmsg
    raise TypeError('Your input type is not a numpy array')
TypeError: Your input type is not a numpy array