class_docstr: Base tracker of single objec tracking 
class_docstr_tok: ["Base","tracker","of","single","objec","tracking"]
docstr: Parameters
  ----------
  img : np.ndarray
      BGR image
  bbox : list
      [x, y, width, height] x, y need to be 0-based
  ctx : mxnet.Context
      Context such as mx.cpu(), mx.gpu(0).
docstr_tok: ["Parameters","--","--","--","--","--","img",":","np.ndarray","BGR","image","bbox",":","list","[","x",",","y",",","width",",","height","]","x",",","y","need","to","be","0-based","ctx",":","mxnet.Context","Context","such","as","mx.cpu","(",")",",","mx.gpu","(","0",")","."]
code: def init(self, img, bbox, ctx):
      """
      Parameters
      ----------
      img : np.ndarray
          BGR image
      bbox : list
          [x, y, width, height] x, y need to be 0-based
      ctx : mxnet.Context
          Context such as mx.cpu(), mx.gpu(0).
      """
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import math
  from collections import namedtuple
  import numpy
  import mxnet
  from mxnet import nd
  from gluoncv.utils.filesystem import try_import_cv2
label_desc: Use image node_id 1 for calling the BaseTracker obj's underlying member method code with example usage: obj.init(img, bbox, ctx) without return types