code: def mass_center(model, data):
      mass = np.expand_dims(model.body_mass, axis=1)
      xpos = data.xipos
      return (np.sum(mass * xpos, axis=0) / np.sum(mass))[0:2].copy()
  
file_path: gym/gym/envs/mujoco/humanoid_v4.py
imports: import numpy
  from gym import utils
  from gym.envs.mujoco import MujocoEnv
  from gym.spaces import Box
label_desc: Use image node_id 1 for calling a global function with example usage: mass_center(model, data) and returns: unknown