Use repo.rev_parse("revspec") to obtain an object hash, and with repo.odb.info(hash) it should be possible to learn what kind of object it is. All objects except for trees can be printed directly. That can probably be done with repo.odb.stream(hash) or maybe there is a method for that on the info object returned earlier.

It's not obvious how to figure that out from the docs, it's hard to discover, and the above will need some experimentation but should give enough hints to figure the details out from there. If in doubt, repo.git.cat_file("revspec", p=true) will definitely do it.