Subscribing to multiple topics from a rosbag [closed]

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I am using a rosbag that publishes various topics and i would like to process those data using a ros node. Is this possible? If so, how? I came across a few codes that tries to synchronise the callback but in this case, i do not need to do so because the rosbag has already synchronised the messages to be published at different time stamps.

The tutorials for ROS only show a single topic for a node which is not what i want to do.