code: def contact_cost(self):
      contact_cost = self._contact_cost_weight * np.sum(
          np.square(self.contact_forces)
      )
      return contact_cost
  
file_path: gym/gym/envs/mujoco/ant_v3.py
imports: import numpy
  from gym import utils
  from gym.envs.mujoco import MuJocoPyEnv
  from gym.spaces import Box
label_desc: Use image node_id 5 for calling the AntEnv obj's underlying member method code with example usage: obj.contact_cost() and returns: contact_cost