code: def switch_psm_to_peptable_fields(oldheader):
      
      return {old: new for old, new in zip([mzidtsvdata.HEADER_PEPTIDE,
                                            mzidtsvdata.HEADER_PROTEIN,
                                            mzidtsvdata.HEADER_PEPTIDE_Q,
                                            mzidtsvdata.HEADER_PEPTIDE_PEP],
                                           [peptabledata.HEADER_PEPTIDE,
                                            peptabledata.HEADER_PROTEINS,
                                            peptabledata.HEADER_QVAL,
                                            peptabledata.HEADER_PEP])}
docs: Returns a dict map with old to new header fields