class_docstr: Base class for instanes that stack job estimators
docstr: Check stack
docstr_tok: ["Check","stack"]
code: def __stack__(self):
      """Check stack"""
      if not isinstance(self.stack, list):
          raise ValueError(
              "Stack corrupted. Extected list. Got %r"
              % type(self.stack)
          )
      return len(self.stack) > 0
  
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 8 for calling the BaseStacker obj's underlying member method code with example usage: obj.__stack__() and returns: unknown