What is the physics engine used by DeepMimic? I found a video for the paper DeepMimic: Example-Guided Deep Reinforcement Learning of Physics-Based Character Skills
 on YouTube.

I looked in the related paper, but could not find details of how to the environment was created, such as the physics engine it used. I would like to use it, or something similar.
Bullet physics engine

Their paper says

Physics simulation is performed at 1.2kHz using the Bullet physics engine [Bullet 2015].