code: @Nullable
    private static String _getAttributeValue (@Nullable final String sAttrValue)
    {
      return sAttrValue == null ? null : sAttrValue.trim ();
    }
docs: Utility method to get a real attribute value, by trimming spaces, if the
  value is non-<code>null</code>.
  
  @param sAttrValue
  The source attribute value. May be <code>null</code>.
  @return <code>null</code> if the input parameter is <code>null</code>.