docs: def loader(self, file_name, bad_steps=None, **kwargs):
          """Loads data from biologics .mpr files.
  
          Args:
              file_name (str): path to .res file.
              bad_steps (list of tuples): (c, s) tuples of steps s
               (in cycle c) to skip loading.
  
          Returns:
              new_tests (list of data objects)
          """
          new_tests = []
          if not os.path.isfile(file_name):
              self.logger.info("Missing file_\n   %s" % file_name)
              return None
  
          filesize = os.path.getsize(file_name)
          hfilesize = humanize_bytes(filesize)
          txt = "Filesize: %i (%s)" % (filesize, hfilesize)
          self.logger.debug(txt)
  
          # creating temporary file and connection
          temp_dir = tempfile.gettempdir()
          temp_filename = os.path.join(temp_dir, os.path.basename(file_name))
          shutil.copy2(file_name, temp_dir)
  
          self.logger.debug("tmp file: %s" % temp_filename)
          self.logger.debug("HERE WE LOAD THE DATA")
  
          data = DataSet()
          fid = FileID(file_name)
  
          # div parameters and information (probably load this last)
          test_no = 1
          data.test_no = test_no
          data.loaded_from = file_name
  
          # some overall prms
          data.channel_index = None
          data.channel_number = None
          data.creator = None
          data.item_ID = None
          data.schedule_file_name = None
          data.start_datetime = None
          data.test_ID = None
          data.test_name = None
          data.raw_data_files.append(fid)
  
          # --------- read raw-data (normal-data) -------------------------
          self.logger.debug("reading raw-data")
          self.mpr_data = None
          self.mpr_log = None
          self.mpr_settings = None
  
          self._load_mpr_data(temp_filename, bad_steps)
          length_of_test = self.mpr_data.shape[0]
          self.logger.debug(f"length of test: {length_of_test}")
  
          self.logger.debug("renaming columns")
          self._rename_headers()
          # ---------  stats-data (summary-data) -------------------------
          summary_df = self._create_summary_data()
  
          if summary_df.empty:
              txt = "\nCould not find any summary (stats-file)!"
              txt += " (summary_df.empty = True)"
              txt += "\n -> issue make_summary(use_cellpy_stat_file=False)"
              warnings.warn(txt)
  
          data.dfsummary = summary_df
          data.dfdata = self.mpr_data
  
          data.raw_data_files_length.append(length_of_test)
          new_tests.append(data)
  
          self._clean_up(temp_filename)
          return new_tests