/*
 * call-seq:
 *  include?(node)
 *
 *  Returns true if any member of node set equals +node+.
 */
static VALUE include_eh(VALUE self, VALUE rb_node)
{
  xmlNodeSetPtr node_set;
  xmlNodePtr node;

  if(!(rb_obj_is_kind_of(rb_node, cNokogiriXmlNode) || rb_obj_is_kind_of(rb_node, cNokogiriXmlNamespace)))
    rb_raise(rb_eArgError, "node must be a Nokogiri::XML::Node or Nokogiri::XML::Namespace");

  Data_Get_Struct(self, xmlNodeSet, node_set);
  Data_Get_Struct(rb_node, xmlNode, node);

  return (xmlXPathNodeSetContains(node_set, node) ? Qtrue : Qfalse);
}