code: def plot_fiber_slice(self, plane=None, index=None, fig=None):
          r
          if hasattr(self, '_fiber_image') is False:
              logger.warning('This method only works when a fiber image exists')
              return
          slice_image = self._get_fiber_slice(plane, index)
          if slice_image is not None:
              if fig is None:
                  plt.figure()
              plt.imshow(slice_image.T, cmap='Greys', origin='lower',
                         interpolation='nearest')
  
          return fig
docs: r"""
          Plot one slice from the fiber image
  
          Parameters
          ----------
          plane : array_like
          List of 3 values, [x,y,z], 2 must be zero and the other must be between
          zero and one representing the fraction of the domain to slice along
          the non-zero axis
  
          index : array_like
          similar to plane but instead of the fraction an index of the image is
          used