This is a library for the mini-dfplayer, a minimalistic MP3-player available for a few bucks from Ebay, Amazon and other distributors.
The chip has a number of pins for direct control, but also an UART-interface and this library controls the chip using the documented commands.
The core of the code is from a micropython implementation of the interface https://github.com/jczic/KT403A-MP3.
Just copy the file lib/DFPlayer.py to your lib-directory on your board.
Import the library and create a DFPlayer-object. If you don't pass an
uart, the constructor uses board.RX and board.TX to create a default.
Use the created object to control the player. For the API just have a
look at the source-code.
A real-world example can be found in the project: https://github.com/bablokb/xmas-music-box.