Publish protobuf message

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Hi Guys,

I am trying to publish custom protobuf message from a ros node.

My protobuffer message format is as given below :

syntax = "proto2";
package proto_tutorial;

message sample {
  required string name = 1;
  required int32 id = 2;
  required double salary = 3;
}

And my talker.py is as given below:

import rospy
from std_msgs.msg import String
import sys

proto_path = "/home/catkin_ws_proto/test/gen_files/"
sys.path.append(proto_path)
import sample_pb2
from sample_pb2 import sample

def talker():
    pub = rospy.Publisher('chatter', sample, queue_size=10)    # How to define the message type
    rospy.init_node('talker', anonymous=True)
    rate = rospy.Rate(10) # 10hz
    while not rospy.is_shutdown():
        hello_str = "hello world %s" % rospy.get_time()
        rospy.loginfo(hello_str)
        pub.publish(hello_str)
        rate.sleep()

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

But I am not able to define the message type in the pub = rospy.Publisher('chatter', sample, queue_size=10), could you please help me in clarifying the below doubts.

1. How can I define the custom message type ?
2. Is this supported ?
3. Is conversion is the only solution ?

Thank you, KK