code: def __len__(self):
      return self.n
  
imports: from nvidia.dali.pipeline import Pipeline
  from nvidia.dali import pipeline_def
  import nvidia.dali.ops
  import nvidia.dali.fn
  import nvidia.dali.types
  import numpy
  import random
label_desc: Use image node_id 2 for calling the BBoxDataIterator obj's underlying member method code with example usage: obj.__len__() and returns: self