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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_item(self, key):
 """ Return the tus url of a file, identified by the key specified. :Args: - key[str]: The unique id for the stored item (in this case, url) :Returns: url[str] """

        result = self._db.search(self._urls.key == key)
        return result[0].get('url') if result else None