docs: def inspect(self, run_data):
          """Inspect the file -> reports to log (debug)"""
  
          # TODO: type checking
          if DEBUG_MODE:
              checked_rundata = []
              for data in run_data:
                  new_cols = data.dfdata.columns
                  for col in self.headers_normal:
                      if col not in new_cols:
                          logging.debug(f"Missing col: {col}")
                          # data.dfdata[col] = np.nan
                  checked_rundata.append(data)
          else:
              checked_rundata = run_data
  
          return checked_rundata