38   history: Object;  property in TransactionHistory
43     this.history = {};
66     const merge = new Merge(originalId, mergedId, this.history);
76     if (!this.history[transactionId]) {
77       this.history[transactionId] = [];
79     this.history[transactionId].push(event);
87     if (!this.history[transactionId]) {
92     const events = this.history[transactionId];
148     return (this.history[transactionId] ?? [])
187   constructor(originalId, mergedId, history) {
192     this.mergedAt = history[mergedId]?.length ?? 0;