Why are there methods that only apply to a few (or even just one) client objects?
In short, some protocols have unique or special features that very few (if not none) other protocols have. A good example is the MODE defined in the FTP protocol standard, which instructs the server to transfer files either as binary or as ASCII text (with automatic EOL conversion). FTP is the only protocol that has such feature, therefore a method was needed for the FTP client object that no other client object can have simply because no other protocol has this feature.
For this reason, occasionally, we find ourselves in need of an extra method that only appears in a certain client object. We document such special methods in this section of the manual.