Transform pose from one frame to another

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I'm using a tensorflow object detector to find and reproject pose estimates for objects in 3D (via a Realsense). I am publishing the local transforms, i.e. /object_n -> /camera_link, but would like to have the 3D locations persist in a SLAM map a la rtabmap. Thus I would like /object_n -> /map

I have looked into tf.TransformROS and tf.TransformListener, but the documentation doesn't include full examples and the examples that do exist are incomplete / misleading.

Currently, I'm not sure how Transform[ROS/Listener] operates. I'm runningif self.tf_listener.frameExists("/camera_link"): ..., which returns false. Running rostopic echo /tf shows that /camera_link is in fact a valid frame.