code: def contract(self, x):
          
          self.active = self.active.contract(x)
          return self.active
docs: 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`.