The annotation format is in a docstring  in the source code:

  

      github.com
  

  
    tensorflow/models/blob/master/research/object_detection/utils/colab_utils.py#L436-L459 6



      
      
          The input of the call back function is a list of list of objects
          corresponding to the annotations. The format of annotations is shown
          below
          
          
[
            // stuff for image 1
            [
              // stuff for rect 1
              {x, y, w, h},
              // stuff for rect 2
              {x, y, w, h},
              ...
            ],
            // stuff for image 2
            [
              // stuff for rect 1
              {x, y, w, h},
              // stuff for rect 2
              {x, y, w, h},
              ...
      
    
  

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