For my gmail source [1] I need to find out the labels for each message in
sup. This is to update the remote Gmail with the labels the user set using
sup.

I am not very familiar with sup source code and my attempts to extract the
message labels based on the message id have failed.

My last try was:

index = Redwood::Index.instance
msg = index.build_message(uid)

but this results in an error about Range not being converted to Integer.
The uid is the id I use to register the message to sup during the poll
method call.

Any tips are appreciated
Horacio

[1] https://github.com/hsanson/sup/tree/gmail_source