addOp(operation) {
    this.ops.push(operation)

    if (operation.action === 'set' && operation.values) {
      this.nextOpNum += operation.values.length
    } else if (operation.action === 'del' && operation.multiOp) {
      this.nextOpNum += operation.multiOp
    } else {
      this.nextOpNum += 1
    }
  }
Adds an operation object to the list of changes made in the current context.