code: def _check_features(features):
      if features is None:
          return [np.mean]
      elif isinstance(features, list) and all(
          [callable(func) for func in features]
      ):
          return features
      else:
          raise ValueError(
              "Features must be list containing only functions (callables) "
              "to be applied to the data columns"
          )
  
imports: import numpy
  import pandas
  from joblib import Parallel, delayed
  from sktime.datatypes import convert_to
  from sktime.transformations.base import BaseTransformer
  from sktime.transformations.panel.segment import RandomIntervalSegmenter
  from sktime.utils.pandas import df_map
label_desc: Use image node_id 1 for calling a global function with example usage: _check_features(features) and returns: list, features