for (Plugin element : tgt) {
                    Object key = getPluginKey().apply(element);
                    master.put(key, element);
                }

                Map<Object, List<Plugin>> predecessors = new LinkedHashMap<>();
                List<Plugin> pending = new ArrayList<>();
                for (Plugin element : src) {
                    Object key = getPluginKey().apply(element);

                        Object key = getPluginKey().apply(plugin);

                        master.put(key, plugin);
                    }
                }

                Map<Object, List<Plugin>> predecessors = new LinkedHashMap<>();
                List<Plugin> pending = new ArrayList<>();
                for (Plugin element : tgt) {
                    Object key = getPluginKey().apply(element);