docs: def _interval_to_double_bound_points(xarray, yarray):
      """
      Helper function to deal with a xarray consisting of pd.Intervals. Each
      interval is replaced with both boundaries. I.e. the length of xarray
      doubles. yarray is modified so it matches the new shape of xarray.
      """
  
      xarray1 = np.array([x.left for x in xarray])
      xarray2 = np.array([x.right for x in xarray])
  
      xarray = list(itertools.chain.from_iterable(zip(xarray1, xarray2)))
      yarray = list(itertools.chain.from_iterable(zip(yarray, yarray)))
  
      return xarray, yarray