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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 length(self):
 """The number of elements changed. :rtype: int .. code:: python assert change.length == len(change.indices) assert change.length == len(change.elements) """

        span = self._stop - self._start
        length, modulo = divmod(span, self._step)
        if length < 0:
            return 0
        if modulo != 0:
            return length + 1
        return length