Adding modelState to gazebo simulator using python node

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Hello,

I would like to add a model to gazebo simulator not in the world file but while executing a node. Therefore, I created the following node:

#!/usr/bin/env python
import rospy  
import roslib
from std_msgs.msg import String
from gazebo_msgs.msg import ModelState


def setObject():

    pub = rospy.Publisher('setObjectTopic', ModelState, queue_size=10)
    rospy.init_node('setObject', anonymous=True)
    rate = rospy.Rate(10) # 10hz
    while not rospy.is_shutdown():
    msg = ModelState() 
    msg.pose.position.x = 1.0 
    msg.pose.position.y = 1.0 
    msg.model_name = "grey_wall"
        pub.publish(msg)
        rate.sleep()
        print  "here"


if __name__ == '__main__':
    try:
         setObject()
    except rospy.ROSInterruptException:
         pass

I didnt git any syntax error but I could not see the object on the gazebo. So, what should I do to make this thing works?