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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 to_atomic(self):
 """ Return the smallest atomic interval containing this interval. :return: an AtomicInterval instance. """

        lower = self._intervals[0].lower
        left = self._intervals[0].left
        upper = self._intervals[-1].upper
        right = self._intervals[-1].right

        return AtomicInterval(left, lower, upper, right)