code: def contact_cost(self):
      contact_forces = self.sim.data.cfrc_ext
      contact_cost = self._contact_cost_weight * np.sum(
          np.square(contact_forces)
      )
      min_cost, max_cost = self._contact_cost_range
      contact_cost = np.clip(contact_cost, min_cost, max_cost)
      return contact_cost
  
file_path: gym/gym/envs/mujoco/humanoid_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 4 for calling the HumanoidEnv obj's underlying member method code with example usage: obj.contact_cost() and returns: contact_cost