The set object for the given full name provided.
A silent object if the field is not found, to allow silent failure.
Retrieves a field set for this post with the given name.
Note: It is more concise to make use of the __get method overloading to retrieve a set, but this method is a fallback when the field name clashes with a known property of the post. A good example is if you name a field set “content” which cannot be retrieved directly on the object since WOOF_Post has a method named content to retrieve the standard post content.