Why are there references to extra "non-existent" links?

[roman-aguilera]

I am using the 2D walker example but I notice this problem happens with other environments as well.

I am trying to change the instantaneous base velocity for a single link using:

env_instance.env._p.resetBaseVelocity(env_instance.env.robot.parts['thigh'].bodyPartIndex, linearVelocity = [0,0,0], angularVelocity=[0,0,0], physicsClientId = env_instance.env._p._client)

However when I type in the following:

import gym
import pybulletgym
env_instance = gym.make("Walker2DBulletEnv-v0", render=True)
env_instance.reset()
env_instance.env.robot.parts

The output gives a list of 17 links, but there should be about 8 max (including the floor):

{'link0_2': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc8e20438>, 'torso': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b710>, 'link0_3': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b5f8>, 'link0_4': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b6a0>, 'link0_6': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b780>, 'thigh': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b860>, 'link0_8': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b908>, 'leg': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657b9e8>, 'link0_10': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657ba58>, 'foot': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bb38>, 'link0_12': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bbe0>, 'thigh_left': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bba8>, 'link0_14': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bcc0>, 'leg_left': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bd68>, 'link0_16': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bdd8>, 'foot_left': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657be80>, 'floor': <pybulletgym.envs.roboschool.robots.robot_bases.BodyPart object at 0x7f1dc657bef0>}