In the online documentation, and in the dns/zones.py file, the methods find_rdataset() and get_rdataset() have the return type (@rtype) listed as "dns.rrset.RRset object", but they actually return "dns.rdataset.Rdataset" objects (as the method names imply).
It is pretty minor, but I ended up wasting some time debugging until I realized that the documentation as incorrect, and found the correct functions.