code: def get_test_data(batch=128):
      ds = dataset.Mnist("test")
      ds = BatchData(ds, batch)
      return ds
  
file_path: tensorpack/examples/SimilarityLearning/embedding_data.py
imports: import numpy
  from tensorpack.dataflow import BatchData, dataset
label_desc: Use image node_id 1 for calling a global function with example usage: get_test_data(batch) and returns: ds