The "Grammars/gra_knotInFrame.gap" is a specialized version of the general grammar gra_pknot_microstate.gap.
It is used by the program KnotInFrame to determine the free energy of specific pseudoknot structures, which can enforce a ribosomal -1 frameshift during translation.
Production rules for the pseudoknot itself are defined in grapart_knotinframe.gap.