Return a collection of filtered nodes.

        Filtered based on the @selector and @not_selector parameters.

def get_nodes_by_selector(self, selector, not_selector=None):
        """Return a collection of filtered nodes.

        Filtered based on the @selector and @not_selector parameters.
        """
        nodes = self.parsed(selector)

        if not_selector is not None:
            nodes = nodes.not_(not_selector)

        return nodes