Does not work for Schema, for CERESomega only if all labels are empty (clauses are correct, but labels forgotten).
The pick* functions generalize the convenience constructors of the LK rules which allow to specify arguments by a formula instead of an index.
The pick* functions generalize the convenience constructors of the LK rules which allow to specify arguments by a formula instead of an index. Here we lookup fitting matches for the auxiliary formulas of each LK rule. In the case of LK, fitting is defined as equality of the formula. In the case of LKsk, it is equality of formulas and skolem labels. An algorithm using pickrule is therefore easier to transfer to LKsk.