code: def get_core_matrix(self, yaw):
      core_matrix = np.zeros(shape=(3, 3))
      core_matrix[0][0] = math.cos(yaw)
      core_matrix[0][2] = -1.0 * math.sin(yaw)
      core_matrix[1][1] = 1
      core_matrix[2][0] = math.sin(yaw)
      core_matrix[2][2] = math.cos(yaw)
      return core_matrix
  
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 PelvisBasedObs obj's underlying member method code with example usage: obj.get_core_matrix(yaw) and returns: core_matrix