docstr: read one track each time
          
docstr_tok: ["read","one","track","each","time"]
code: def read_track(self):
      """read one track each time"""
      off0, off1 = self.offsets[self.offs_pos : self.offs_pos + 2]
      self.offs_pos += 1
      return self.tracks[off0:off1]
  
file_path: dipy/dipy/io/dpy.py
imports: import numpy
  import h5py
  from nibabel.streamlines import ArraySequence
label_desc: Use image node_id 5 for calling the Dpy obj's underlying member method code with example usage: obj.read_track() and returns: self