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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(self, line_number):
 """Return the needle positions or None. :param int line_number: the number of the line :rtype: list :return: the needle positions for a specific line specified by :paramref:`line_number` or :obj:`None` if no were given """

        if line_number not in self._get_cache:
            self._get_cache[line_number] = self._get(line_number)
        return self._get_cache[line_number]