public ProofStepChainReduction(Chain reduction, Chain nearParent,
Chain farParent, Dictionary<Variable, Term> subst)
{
this.reduction = reduction;
this.nearParent = nearParent;
this.farParent = farParent;
this.subst = subst;
this.predecessors.Add(farParent.getProofStep());
this.predecessors.Add(nearParent.getProofStep());
}