code: def _combine_var(
      pred_results,
      local_results,
      axis=0,
      alpha=None,
      alpha_ignore_na=False,
      pred_exponent=None,
  ):
      local_results[0] = local_results[0].ffill()
      alpha_data = local_results[1]
      local_results[1] = alpha_data.ffill()
  
      local_results[2] = local_results[2].ffill()
      alpha2_data = local_results[3]
      local_results[3] = alpha2_data.ffill()
  
      (
          local_sum_data,
          local_count_data,
          local_sum_square,
          local_count2_data,
      ) = local_results
      if pred_results is None:
          return (
              local_sum_square - local_sum_data**2 / local_count_data
          ) / (local_count_data - local_count2_data / local_count_data)
  
      (
          pred_sum_data,
          pred_count_data,
          pred_sum_square,
          pred_count2_data,
      ) = pred_results
  
      (local_count2_data,) = _add_pred_results(
          [pred_count2_data],
          [local_count2_data],
          axis=axis,
          alpha=alpha,
          order=2,
          alpha_ignore_na=alpha_ignore_na,
          pred_exponent=pred_exponent,
          alpha_data=alpha_data,
      )
  
      (
          local_sum_square,
          local_sum_data,
          local_count_data,
      ) = _add_pred_results(
          [pred_sum_square, pred_sum_data, pred_count_data],
          [local_sum_square, local_sum_data, local_count_data],
          axis=axis,
          alpha=alpha,
          alpha_ignore_na=alpha_ignore_na,
          pred_exponent=pred_exponent,
          alpha_data=alpha_data,
      )
  
      return (
          local_sum_square - local_sum_data**2 / local_count_data
      ) / (local_count_data - local_count2_data / local_count_data)
  
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 3 for calling a global function with example usage: _combine_var(pred_results, local_results, axis, alpha, alpha_ignore_na, pred_exponent) and returns: unknown, unknown