buffer -- a gtk:text-buffer object the format is registered with
content -- a gtk:text-buffer object to deserialize into
iter -- a gtk:text-iter insertion point for the deserialized text
data -- a pointer to the data to deserialize
create -- true if deserializing may create tags
result -- true on success, false otherwise

A function that is called to deserialize rich text that has been serialized with the gtk:text-buffer-serialize function, and insert it at iter.