How to create a rosbag file with messages with an header

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Hi,

As I wrote on the title I'm trying to create a rosbag file from another one changing message types and using only some topics from the original one. The problem is, when I play the new rosbag the messages type is Float32, thus headerless.

Does someone know how can I write messages with an header (Float32Stamped or what else) in the new rosbag, without any error? I read that the last parameter of the write function is connection_header, but I didn't find anything that explain something about it. In the following, the code.

Thank you for the help

#!/usr/bin/env python3
import rosbag
from marti_common_msgs.msg import Float32Stamped


with rosbag.Bag('try.bag', 'w') as outbag:
    for topic, msg, t in rosbag.Bag('20180810150607_bus_signals.bag').read_messages():
        if '/value' in topic:
            fmsg = Float32Stamped()
            fmsg.header = t
            fmsg.value = msg
            outbag.write(topic,fmsg.value, fmsg.header if fmsg._has_header else t)
        else:
            continue    
outbag.close()