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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_pages(self, label=None):
 """Returns list of pages with specified label."""

        return (
            page for page in sorted(
                self._pages.values(), key=lambda i: i.created, reverse=True
            ) if ((not label or label in page.labels) and page.visible)
        )