code: @Nonnull
    public DataTablesDom addCustom (@Nonnull @Nonempty final String sStr)
    {
      ValueEnforcer.notEmpty (sStr, "Str");
      _internalAdd (sStr);
      return this;
    }
docs: Add a custom element
  
  @param sStr
  Custom element to add. May not be <code>null</code> nor empty.
  @return this