code: private Stream<ImportSnippet> importSnippets() {
          return state.keyMap.importKeys()
                  .map(key -> (ImportSnippet)getSnippet(key))
                  .filter(sn -> sn != null && state.status(sn).isDefined());
      }
docs: Compute the set of imports to prepend to a snippet
  @return a stream of the import needed