code: protected void removeCachedExtensionVersion(String feature, E extension)
      {
          // versions
          List<E> extensionVersions = this.extensionsVersions.get(feature);
          extensionVersions.remove(extension);
          if (extensionVersions.isEmpty()) {
              this.extensionsVersions.remove(feature);
          }
      }
docs: Remove passed extension associated to passed feature from the cache.
  
  @param feature the feature associated to the extension
  @param extension the extension