class_docstr: Customized target trajectory here, it support 3 ways currently
  1.fixed_speed, e.g. reset(.., fixed_speed=1.25)
  2.stage , e.g. reset(.., stage=1)
  3.boundary, e.g. reset(.., boundary=True)
class_docstr_tok: ["Customized","target","trajectory","here",",","it","support","3","ways","currently","1.fixed_speed",",","e.g",".","reset","(","..",",","fixed_speed=1.25",")","2.stage",",","e.g",".","reset","(","..",",","stage=1",")","3.boundary",",","e.g",".","reset","(","..",",","boundary=True",")"]
code: def rect(self, row):
      r = row[0]
      theta = row[1]
      x = r * math.cos(theta)
      y = 0
      z = r * math.sin(theta)
      return np.array([x, y, z])
  
imports: import abc
  import gym
  import math
  import numpy
  import random
  from collections import OrderedDict
  from osim.env import ProstheticsEnv
  from parl.utils import logger
  from tqdm import tqdm
label_desc: Use image node_id 2 for calling the CustomR2Env obj's underlying member method code with example usage: obj.rect(row) and returns: np