1const READ_DOCUMENTATION ; 
2https://docs.mongodb.com/manual/reference/command/findAndModify/#lasterrorobject
3
4The lastErrorObject embedded document contains the following fields:
5//updatedExisting boolean
6  true if an update operation modified an existing document.
7//upserted document
8	Contains the ObjectId of the inserted document if an update operation with upsert: true resulted in a new document.
9//Value
10	For /*remove*/ operations, value contains the removed document 
11    if the query matches a document.
12    If the query does not match a document to remove,
13      value contains null.
14
15	For /*update*/ operations, the value embedded document contains 
16    the following:
17
18	If the new parameter is not set or is false:
19
20    the pre-modification document if the query matches a document;
21    otherwise, null.
22    If new is true:
23
24    the modified document if the query returns a match;
25    the inserted document if upsert: true and no document matches
26    the query;otherwise, null.