code: public @CheckForNull Plugin getPlugin(String artifactId) {
          for (UpdateSite s : sites) {
              Plugin p = s.getPlugin(artifactId);
              if (p!=null) return p;
          }
          return null;
      }
docs: Gets the plugin with the given name from the first {@link UpdateSite} to contain it.
  @return Discovered {@link Plugin}. {@code null} if it cannot be found