class_docstr: Load the subdataset for tracking.
  get annotation data,and get positive pair every frame range.
  
  Parameters
  ----------
  name : str
      dataset name.
  root : str
      Path to the folder stored the dataset.
  anno : str
      Path to the Json stored detaset annotation
  frame_range : int
      dataset frame range that get positive pair.
  num_use : int
      if num_use = -1 show all dataset,show fisrt num_use dataset
  start_idx : int
      dataset start idx
class_docstr_tok: ["Load","the","subdataset","for","tracking",".","get","annotation","data",",","and","get","positive","pair","every","frame","range",".","Parameters","--","--","--","--","--","name",":","str","dataset","name",".","root",":","str","Path","to","the","folder","stored","the","dataset",".","anno",":","str","Path","to","the","Json","stored","detaset","annotation","frame_range",":","int","dataset","frame","range","that","get","positive","pair",".","num_use",":","int","if","num_use","=","-1","show","all","dataset",",","show","fisrt","num_use","dataset","start_idx",":","int","dataset","start","idx"]
docstr: get image annotation
  
  Parameters
  ----------
      video : str
          video name
      track : str
          track number
      frame : str
          frame number
  Returns
      image_path and image bbox
docstr_tok: ["get","image","annotation","Parameters","--","--","--","--","--","video",":","str","video","name","track",":","str","track","number","frame",":","str","frame","number","Returns","image_path","and","image","bbox"]
code: def get_image_anno(self, video, track, frame):
      """get image annotation
  
      Parameters
      ----------
          video : str
              video name
          track : str
              track number
          frame : str
              frame number
      Returns
          image_path and image bbox
      """
      frame = "{:06d}".format(frame)
      image_path = os.path.join(
          self.root, video, self.path_format.format(frame, track, "x")
      )
      image_anno = self.labels[video][track][frame]
      return image_path, image_anno
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import json
  import logging
  import os
  import numpy
  from mxnet.gluon.data import dataset
  from gluoncv.utils.filesystem import try_import_cv2
  from gluoncv.model_zoo.siamrpn.siamrpn_tracker import corner2center, center2corner
  from gluoncv.model_zoo.siamrpn.siamrpn_tracker import Center, Anchors
  from gluoncv.data.transforms.track import SiamRPNaugmentation
  from gluoncv.utils.bbox import bbox_iou
label_desc: Use image node_id 5 for calling the SubDataset obj's underlying member method code with example usage: obj.get_image_anno(video, track, frame) and returns: image_path,  image_anno