class_docstr: Wraps a mock image array and provide a needed getdata() interface function. 
code: def getdata(self):
      return self.a
  
file_path: petastorm/examples/mnist/tests/conftest.py
imports: import numpy
  import pytest
label_desc: Use image node_id 2 for calling the MockDataObj obj's underlying member method code with example usage: obj.getdata() and returns: self