code: public Set<String> getCustomPlugins(boolean enabled){
          Set<Entry<String, Boolean>> entrySet = customPlugins.entrySet();
          Set<String> result = new TreeSet<>();
          for (Entry<String, Boolean> entry : entrySet) {
              if(enabled) {
                  if(entry.getValue() != null && entry.getValue().booleanValue()) {
                      result.add(entry.getKey());
                  }
              } else {
                  if(entry.getValue() == null || !entry.getValue().booleanValue()) {
                      result.add(entry.getKey());
                  }
              }
          }
          return result;
      }
docs: Additional plugins which could be used or shouldn't be used (depending on
  given argument) by {@link IFindBugsEngine}. If a plugin is not included
  in the set, it's enablement depends on it's default settings.
  
  @return set with additional third party plugins, might be empty, never
  null. The elements are either absolute plugin paths or plugin id's.
  <b>Special case</b>: if the path consists of one path segment
  then it represents the plugin id for a plugin to be
  <b>disabled</b>.
  @see Plugin#isCorePlugin()
  @see Plugin#isGloballyEnabled()