regexp list-topic topic-level)
"List all newsgroups with unread articles of level LEVEL or lower.
Use the `gnus-group-topics' to sort the groups.
-If PREDICTE is a function, list groups that the function returns non-nil;
+If PREDICATE is a function, list groups that the function returns non-nil;
if it is t, list groups that have no unread articles.
If LOWEST is non-nil, list all newsgroups of level LOWEST or higher."
(set-buffer gnus-group-buffer)