public function testAddToSequenceInPositionAgain()
 {
     $graph = new ExtendedGraph();
     $graph->add_resource_to_sequence('http://seq', 'http://item/1');
     $graph->add_resource_to_sequence('http://seq', 'http://item/2');
     $graph->add_resource_to_sequence('http://seq', 'http://item/3');
     $graph->add_resource_to_sequence('http://seq', 'http://item/4');
     $graph->add_resource_to_sequence_in_position('http://seq', 'http://item/new', 2);
     $this->assertTrue($graph->has_resource_triple('http://seq', ExtendedGraph::rdf . '_1', 'http://item/1'));
     $this->assertTrue($graph->has_resource_triple('http://seq', ExtendedGraph::rdf . '_2', 'http://item/new'));
     $this->assertTrue($graph->has_resource_triple('http://seq', ExtendedGraph::rdf . '_3', 'http://item/2'));
     $this->assertTrue($graph->has_resource_triple('http://seq', ExtendedGraph::rdf . '_4', 'http://item/3'));
     $this->assertTrue($graph->has_resource_triple('http://seq', ExtendedGraph::rdf . '_5', 'http://item/4'));
 }