class_docstr: Base class for instanes that stack job estimators
code: def __iter__(self):
      yield
  
imports: import warnings
  from abc import abstractmethod
  import numpy
  from ._base_functions import check_stack, check_params
  from ..None import config
  from ..utils.exceptions import ParallelProcessingError
  from ..externals.sklearn.base import clone, BaseEstimator
label_desc: Use image node_id 2 for calling the BaseStacker obj's underlying member method code with example usage: obj.__iter__() without return types