code: def xline(self):
          
          if self.unstructured:
              raise ValueError(self._unstructured_errmsg)
  
          if self._xline is not None:
              return self._xline
  
          self._xline = Line(self,
                             self.xlines,
                             self._xline_length,
                             self._xline_stride,
                             self.offsets,
                             'crossline',
                            )
          return self._xline
docs: Interact with segy in crossline mode
  
          Returns
          -------
          xline : Line or None
  
          Raises
          ------
          ValueError
              If the file is unstructured
  
          Notes
          -----
          .. versionadded:: 1.1