code: def set_epoch(self, epoch):
          
          scale = self.get_xscale()
          return self.set_xscale(scale, epoch=epoch)
docs: Set the epoch for the current GPS scale.
  
          This method will fail if the current X-axis scale isn't one of
          the GPS scales. See :ref:`gwpy-plot-gps` for more details.
  
          Parameters
          ----------
          epoch : `float`, `str`
              GPS-compatible time or date object, anything parseable by
              :func:`~gwpy.time.to_gps` is fine.