et for the specified changes.
 *
 * Some requirements for the optional parameters:
 *
 * * Either childList, attributes or characterData must be true.
 * * If attributeOldValue is true then attributes must also be true.
 * * If attributeFilter is specified then attributes must be true.
 * * If characterDataOldValue is true then characterData must be true.
 */
void observe(Node target,
             {bool childList,
              bool attributes,
              bool characterData,
              bool subtree,
 