    /*
     * 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);
    }