class_docstr: Output Mixin
  
  Mixin class for interfacing with ParallelProcessing when outputs are
  desired.
  
  .. note::
     To use this mixin the instance inheriting it must set the
     ``feature_span`` attribute and ``__no_output__`` flag in ``__init__``.
docstr: Get size of dim 0
docstr_tok: ["Get","size","of","dim","0"]
code: def size(self, attr):
      """Get size of dim 0"""
      if attr not in ["n_test_samples", "n_samples"]:
          attr = "n_test_samples" if attr != "predict" else "n_samples"
  
      indexers = self._get_indexers()
      sizes = list()
      for indexer in indexers:
          sizes.append(getattr(indexer, attr))
  
      sizes = np.unique(sizes)
      if not sizes.shape[0] == 1:
          warnings.warn(
              "Inconsistent output sizes generated by indexers "
              "(sizes: %r from indexers %r).\n"
              "outputs will be zero-padded" % (sizes.tolist(), indexers)
          )
          return max(sizes)
      return sizes[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 4 for calling the OutputMixin obj's underlying member method code with example usage: obj.size(attr) and returns: sizes, max