class_docstr: CocoWholeBody dataset for top-down hand pose estimation. 
  
  The dataset loads raw features and apply specified transforms
  to return a dict containing the image tensors and other information.
  
  COCO-WholeBody Hand keypoint indexes:
  
      0: 'wrist',
      1: 'thumb1',
      2: 'thumb2',
      3: 'thumb3',
      4: 'thumb4',
      5: 'forefinger1',
      6: 'forefinger2',
      7: 'forefinger3',
      8: 'forefinger4',
      9: 'middle_finger1',
      10: 'middle_finger2',
      11: 'middle_finger3',
      12: 'middle_finger4',
      13: 'ring_finger1',
      14: 'ring_finger2',
      15: 'ring_finger3',
      16: 'ring_finger4',
      17: 'pinky_finger1',
      18: 'pinky_finger2',
      19: 'pinky_finger3',
      20: 'pinky_finger4'
  
  Args:
      dataset_dir (str): Root path to the dataset.
      image_dir (str): Path to a directory where images are held.
      anno_path (str): Relative path to the annotation file.
      num_joints (int): Keypoint numbers
      trainsize (list):[w, h] Image target size
      transform (composed(operators)): A sequence of data transforms.
      pixel_std (int): The pixel std of the scale
          Default: 200.
code: def _box2cs(self, box):
      x, y, w, h = box[:4]
      center = np.zeros((2), dtype=np.float32)
      center[0] = x + w * 0.5
      center[1] = y + h * 0.5
      aspect_ratio = self.trainsize[0] * 1.0 / self.trainsize[1]
  
      if w > aspect_ratio * h:
          h = w * 1.0 / aspect_ratio
      elif w < aspect_ratio * h:
          w = h * aspect_ratio
      scale = np.array(
          [w * 1.0 / self.pixel_std, h * 1.0 / self.pixel_std],
          dtype=np.float32,
      )
      if center[0] != -1:
          scale = scale * 1.25
  
      return center, scale
  
imports: import os
  import cv2
  import numpy
  import json
  import copy
  import pycocotools
  from pycocotools.coco import COCO
  from .dataset import DetDataset
  from ppdet.core.workspace import register, serializable
label_desc: Use image node_id 2 for calling the KeypointTopDownCocoWholeBodyHandDataset obj's underlying member method code with example usage: obj._box2cs(box) and returns: center,  scale