docs: def _interp1d(self):
          """Interpolate in one dimension.
          """
          lines = len(self.hrow_indices)
  
          for num, data in enumerate(self.tie_data):
              self.new_data[num] = np.empty((len(self.hrow_indices),
                                             len(self.hcol_indices)),
                                            data.dtype)
  
              for cnt in range(lines):
                  tck = splrep(self.col_indices, data[cnt, :], k=self.ky_, s=0)
                  self.new_data[num][cnt, :] = splev(
                      self.hcol_indices, tck, der=0)