compute degree lift function here in ofcm.m2

	       opts.DegreeLift = (
		    if lm === null then (
			 if dm === identity then (
		    	      d -> (
			 	   for i from #N0 to #M0-1 do if d#i =!= 0 then degreeNoLift();
			 	   drop(d,#M0-#N0)))
	       		 else x -> error "degree lift function not provided (DegreeLift option)")
		    else lm);

as we do here in ringmap.m2

     deglift := (
	  if opts.DegreeLift =!= null then opts.DegreeLift
	  else if degmap === identity then identity
	  else if degreeLength S === 0 and degreeLength R === 0 then identity
	  else (d -> (
		    (q,r) := quotientRemainder(transpose matrix {q}, degmapmatrix);
		    if r != 0 then error "degreeLift: degree not liftable";
		    flatten entries q)));
