Queries the known snippets for the first matching @group, @language_id, and/or @trigger.
If @group or @language_id are %NULL, they will be ignored.
a group name or %NULL
a #GtkSourceLanguage:id or %NULL
the trigger for the snippet
a #GtkSourceSnippet or %NULL if no matching snippet was found.
See Implementation
Queries the known snippets for the first matching @group, @language_id, and/or @trigger.
If @group or @language_id are %NULL, they will be ignored.