code: def _combine_std(pred_results, local_results, axis=0):
      return np.sqrt(
          _combine_var(pred_results, local_results, axis=axis)
      )
  
imports: from collections import namedtuple
  from functools import partial
  import numpy
  import pandas
  from ....None import opcodes
  from ....serialization.serializables import BoolField
  from ..aggregation import BaseDataFrameExpandingAgg
label_desc: Use image node_id 6 for calling a global function with example usage: _combine_std(pred_results, local_results, axis) and returns: np