'Retrieves the first image in the \'top_node\'
The top node is essentially the HTML markdown where the main
article lies and the first image in that area is probably signifigcant.'

def get_first_img_url(self, article_url, top_node):

    node_images = self.get_img_urls(article_url, top_node)
    node_images = list(node_images)
    if node_images:
        return urljoin(article_url, node_images[0])
    return ''
