if (!visited.contains(v)) {
                dropList.add(v);
            }
        }

        if (dropList.size() < 1) {
            return g;
        }

        // now - drop vertices
        TreeSet<MetadataGraphVertex> vertices = g.getVertices();
        for (MetadataGraphVertex v : dropList) {
            vertices.remove(v);
        }

        return g;
    }

 * <li>error - no model, but diagnostics
 * <li>error - (partial) model and diagnostics
 * </ol>
 * Could encode these variants as subclasses, but kept in one for now
 *
 * @param <T> the model type
 */
public class Result<T> {

    /**
     * Success without warnings
     *
     * @param model
     */
    public static <T> Result<T> success(T model) {

        } catch (PluginResolutionException e) {
            logger.debug("Ignoring unresolvable plugin version {}", version, e);
            return false;
        } catch (Exception e) {
            // ignore for now and delay failure to higher level processing
            return true;
        }

        try {
            pluginManager.checkPrerequisites(pluginDescriptor);
        } catch (Exception e) {