Schema.clone() removes prototypes with new Mongoose().

[chumager]

Do you want to request a feature or report a bug?
Bug
What is the current behavior?
If you use Schema.clone(), the functions defined as prototype get removed from cloned schema.
If the current behavior is a bug, please provide the steps to reproduce.

"use strict";
const mongoose = require("mongoose");
const db = new mongoose.Mongoose();
db.Schema.prototype.localTest = function () {
  console.log("prototype");
};
const test = new db.Schema({});
console.log(test.localTest);
const test2 = test.clone();
console.log(test2.localTest);

result:

[Function (anonymous)]
undefined

If you use mongoose directly it works...

Besides this problem I always use new Mongoose() to isolate, is that correct? I need to keep separated different plugins, models and modifications for each mongoose

What is the expected behavior?
To be able to clone schemas and keep the prototype functions.
What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
node: 14.10.1
mongoose: 5.10.5
mongodb: not even connected.