code: def execute(cls, ctx, op: "DataFrameStack"):
      inp: pd.DataFrame = ctx[op.input_df.key]
      ctx[op.outputs[0].key] = inp.stack(
          level=op.level, dropna=op.dropna
      )
  
imports: from typing import Union, List
  import numpy
  import pandas
  from ...None import opcodes
  from ...core import recursive_tile
  from ...serialization.serializables import KeyField, AnyField, BoolField
  from ...utils import has_unknown_shape
  from ..operands import DataFrameOperand, DataFrameOperandMixin
  from ..utils import build_df, parse_index
label_desc: Use image node_id 9 for calling the DataFrameStack obj's underlying member method code with example usage: obj.execute(cls, ctx, op) without return types