* `target` {string} Name of the target database. This can be `'main'` (the default primary database) or any other

database that have been added with [`ATTACH DATABASE`][] **Default:** `'main'`.

* `rate` {number} Number of pages to be transmitted in each batch of the backup. **Default:** `100`.

* `progress` {Function} An optional callback function that will be called after each backup step. The argument passed

to this callback is an {Object} with `remainingPages` and `totalPages` properties, describing the current progress

of the backup operation.

* Returns: {Promise} A promise that fulfills with the total number of backed-up pages upon completion, or rejects if an

error occurs.

This method makes a database backup. This method abstracts the [`sqlite3_backup_init()`][], [`sqlite3_backup_step()`][]

and [`sqlite3_backup_finish()`][] functions.