in pybulletX/robot.py [0:0]
def _get_free_joint_indices(self):
"""
Exclude all fixed joints and return a list of free joint indices
"""
joint_infos = [self.get_joint_info(i) for i in range(self.num_joints)]
return [
info.joint_index for info in joint_infos if info.joint_type != p.JOINT_FIXED
]