code: def _combine_std(
      pred_results,
      local_results,
      axis=0,
      alpha=None,
      alpha_ignore_na=False,
      pred_exponent=None,
  ):
      return np.sqrt(
          _combine_var(
              pred_results,
              local_results,
              axis=axis,
              alpha=alpha,
              alpha_ignore_na=alpha_ignore_na,
              pred_exponent=pred_exponent,
          )
      )
  
imports: from collections import namedtuple
  import numpy
  import pandas
  from ....None import opcodes
  from ....serialization.serializables import BoolField, Float64Field
  from ..aggregation import BaseDataFrameExpandingAgg
label_desc: Use image node_id 4 for calling a global function with example usage: _combine_std(pred_results, local_results, axis, alpha, alpha_ignore_na, pred_exponent) and returns: np