code: def apply_mflist_budget_obs(list_filename,flx_filename="flux.dat",
                              vol_filename="vol.dat",
                              start_datetime="1-1-1970"):
      
      try:
          import flopy
      except Exception as e:
          raise Exception("error import flopy: {0}".format(str(e)))
      mlf = flopy.utils.MfListBudget(list_filename)
      flx,vol = mlf.get_dataframes(start_datetime=start_datetime,diff=True)
      flx.to_csv(flx_filename,sep=' ',index_label="datetime",date_format="%Y%m%d")
      vol.to_csv(vol_filename,sep=' ',index_label="datetime",date_format="%Y%m%d")
      return flx,vol
docs: process a MODFLOW list file to extract flux and volume water budget entries.
  
      Parameters
      ----------
      list_filename : str
          the modflow list file
      flx_filename : str
          the name of the output file with water budget flux information.
          Default is "flux.dat"
      vol_filename : str
          the name of the output file with water budget volume information.
          Default is "vol.dat"
      start_datatime : str
          an str that can be cast to a pandas.TimeStamp.  Used to give
          observations a meaningful name
  
      Returns
      -------
      flx : pandas.DataFrame
          the flux dataframe
      vol : pandas.DataFrame
          the volume dataframe
  
      Note
      ----
      requires flopy