code: def _execute_combine(cls, ctx, op: "DataFrameEwmAgg"):
      try:
          cls._exec_cache[op.key] = dict()
  
          if len(op.inputs) != 1:
              pred_data = ctx[op.inputs[1].key]
  
              if op.alpha_ignore_na:
                  pred_exponent = (
                      pred_data[-2]
                      .shift(-1)[::-1]
                      .cumsum()[::-1]
                      .fillna(0)
                  )
              else:
                  succ_counts = pred_data[-1].shift(-1)
                  succ_counts.iloc[-1] = 0
                  pred_exponent = pred_data[-2].add(
                      succ_counts[::-1].cumsum()[::-1], axis=op.axis
                  )
  
              cls._exec_cache[op.key]["pred_exponent"] = pred_exponent
  
          super()._execute_combine(ctx, op)
      finally:
          cls._exec_cache.pop(op.key, None)
  
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 14 for calling the DataFrameEwmAgg obj's underlying member method code with example usage: obj._execute_combine(cls, ctx, op) without return types