/**
  * Get the value of the given option, as an RDF node. If the option is not defined locally, return
  * the value of the same option of the parent, if the parent is non-null. Otherwise, return <code>
  * null</code>
  *
  * @param option The name of the option to retrieve
  * @return The value of the option as an RDFNode, or null if the option is not defined. If the
  *     parent is non-null and the option is not defined, delegate the <code>getOption</code> to
  *     the parent.
  * @return The RDFnode value of the option, or null
  */
 public RDFNode getOption(OPT option) {
   RDFNode v = getValue(option);
   return (v != null) ? v : (parent != null ? parent.getOption(option) : null);
 }
 /**
  * Get the value of the given option, as a string. If the option is not defined locally, return
  * the value of the same option of the parent, if the parent is non-null. Otherwise, return <code>
  * null</code>
  *
  * @param option The name of the option to retrieve
  * @return The value of the option as a string, or null if the option is not defined. If the
  *     parent is non-null and the option is not defined, delegate the <code>getOption</code> to
  *     the parent.
  * @return The string value of the option, or null
  */
 public String getStringOption(OPT option) {
   String v = getStringValue(option);
   return (v != null) ? v : (parent != null ? parent.getStringOption(option) : null);
 }