docs: def export_to_crtomo_seit_manager(self, grid):
          """Return a ready-initialized seit-manager object from the CRTomo
          tools. This function only works if the crtomo_tools are installed.
          """
          import crtomo
          g = self.data.groupby('frequency')
          seit_data = {}
          for name, item in g:
              print(name, item.shape, item.size)
              if item.shape[0] > 0:
                  seit_data[name] = item[
                      ['a', 'b', 'm', 'n', 'r', 'rpha']
                  ].values
          seit = crtomo.eitMan(grid=grid, seit_data=seit_data)
          return seit