code: def try_run_inschek(pst):
      
      for ins_file,out_file in zip(pst.instruction_files,pst.output_files):
          df = _try_run_inschek(ins_file,out_file)
          if df is not None:
              pst.observation_data.loc[df.index, "obsval"] = df.obsval
docs: attempt to run INSCHEK for each instruction file, model output
      file pair in a pyemu.Pst.  If the run is successful, the INSCHEK written
      .obf file is used to populate the pst.observation_data.obsval attribute
  
      Parameters
      ----------
      pst : (pyemu.Pst)