docs: def import_sip04(self, filename, timestep=None):
          """SIP04 data import
  
          Parameters
          ----------
          filename: string
              Path to .mat or .csv file containing SIP-04 measurement results
  
          Examples
          --------
  
          ::
  
              import tempfile
              import reda
              with tempfile.TemporaryDirectory() as fid:
                  reda.data.download_data('sip04_fs_01', fid)
                  sip = reda.SIP()
                  sip.import_sip04(fid + '/sip_dataA.mat')
  
          """
          df = reda_sip04.import_sip04_data(filename)
          if timestep is not None:
              print('adding timestep')
              df['timestep'] = timestep
  
          self._add_to_container(df)
          print('Summary:')
          self._describe_data(df)