code: def __len__(self):
      return self.n
  
imports: import functools
  import numpy
  import nvidia.dali.fn
  import nvidia.dali.ops
  from nvidia.dali import Pipeline
  from nose_utils import assert_raises
  from test_utils import check_output
label_desc: Use image node_id 2 for calling the TestIteratorZeroCopy obj's underlying member method code with example usage: obj.__len__() and returns: self