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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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