// internal methods
 internal BulkWriteError WithMappedIndex(IndexMap indexMap)
 {
     var mappedIndex = indexMap.Map(_index);
     return (_index == mappedIndex) ? this : new BulkWriteError(mappedIndex, Code, Message, Details);
 }
 // internal methods
 internal BulkWriteUpsert WithMappedIndex(IndexMap indexMap)
 {
     var mappedIndex = indexMap.Map(_index);
     return (_index == mappedIndex) ? this : new BulkWriteUpsert(mappedIndex, _id);
 }