1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
'use strict';
/*! * ignore */
module.exports = function addIdGetter(schema) {  // ensure the documents receive an id getter unless disabled  const autoIdGetter = !schema.paths['id'] &&    schema.paths['_id'] &&    schema.options.id;  if (!autoIdGetter) {    return schema;  }
  schema.virtual('id').get(idGetter);
  return schema;};
/** * Returns this documents _id cast to a string. * @api private */
function idGetter() {  if (this._id != null) {    return String(this._id);  }
  return null;}