code: def get_observation(self, state_desc):
      obs = self._get_observation(state_desc)
      if not isinstance(self, PelvisBasedObs):
          (
              cur_vel_x,
              cur_vel_z,
              diff_vel_x,
              diff_vel_z,
              diff_vel,
              diff_theta,
          ) = calc_vel_diff(state_desc)
          obs = np.append(
              obs,
              [
                  cur_vel_x,
                  cur_vel_z,
                  diff_vel_x,
                  diff_vel_z,
                  diff_vel,
                  diff_theta,
              ],
          )
      else:
          pass
      return obs
  
imports: import abc
  import copy
  import gym
  import math
  import numpy
  from collections import OrderedDict
  from osim.env import ProstheticsEnv
  from parl.utils import logger
label_desc: Use image node_id 2 for calling the ObsTranformerBase obj's underlying member method code with example usage: obj.get_observation(state_desc) and returns: obs