'This method is called for the nodes matching the provided tag name
(itertag). Receives the response and an Selector for each node.
Overriding this method is mandatory. Otherwise, you spider won\'t work.
This method must return either a BaseItem, a Request, or a list
containing any of them.'

def parse_nodes(self, response, nodes):

    for selector in nodes:
        ret = iterate_spider_output(self.parse_node(response, selector))
        for result_item in self.process_results(response, ret):
            (yield result_item)
