<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def contract(self, x):
 """Contract each of the `active` `Segments` by ``x`` seconds. This method adds ``x`` to each segment's lower bound, and subtracts ``x`` from the upper bound. The :attr:`~DataQualityFlag.active` `SegmentList` is modified in place. Parameters x : `float` number of seconds by which to contract each `Segment`. """

        self.active = self.active.contract(x)
        return self.active