public ProductionKey(SymbolId productionSymbolId, SymbolIdSequence ruleSymbolIds)
 {
     this.ProductionSymbolId = productionSymbolId;
     this.RuleSymbolIds      = ruleSymbolIds;
 }
 public ProductionRule(int index, SymbolId productionSymbolId, SymbolIdSequence ruleSymbolIds)
 {
     this.Index = index;
     this.ProductionSymbolId = productionSymbolId;
     this.RuleSymbolIds      = ruleSymbolIds;
 }