[plt-scheme] MrEd - pasteboard - save-file question

Hi all,

I'm building a GUI application with MrEd that builds upon pasteboard
with the graph-pasteboard-mixin. I can save and load just fine with a
vanilla pasteboard, but not with my own classes. Unfortunately the
documentation doesn't make much sense to me. Section 8.2.1 of the MrEd
manual says:

> To convert a snip from an encoded representation (e.g., as bytes in a
file) to a memory object, a decoding function must be provided for each
type of snip

That would only make sense if I also provide an encoding function. How
else do I know how to decode the data again? I found some code that
implements a snip-class and defines a (read) method, but I don't quite
know what I should be reading?

Any help much appreciated,

Chris