docs: def _interp(self, data):
          """The interpolation method implemented here is a kind of a billinear
          interpolation. The input *data* field is first interpolated along the 
          rows and subsequently along its columns.
  
          The final size of the interpolated *data* field is determined by the 
          last indices in self.row_indices and self.col_indices.
          """
          row_interpol_data = self._interp_axis(data, 0)
          interpol_data = self._interp_axis(row_interpol_data, 1)
  
          return interpol_data