code: @Nullable
    public static <E extends AbstractFunction> E findForClass(@Nonnull final Class<E> functionClass) {
      E result = null;
      for (final AbstractFunction function : getAllFunctions()) {
        if (function.getClass() == functionClass) {
          result = functionClass.cast(function);
          break;
        }
      }
      return result;
    }
docs: Allows to find a function handler instance for its class
  
  @param <E>           the class of the needed function handler extends the
  AbstractFunction class
  @param functionClass the class of the needed handler, must not be null
  @return an instance of the needed handler or null if there is not any such
  one