docstr: Map stage implement.
  
  Parameters
  -------
  op : Any operand
      DataFrame operand.
  in_data : pd.DataFrame
      Input dataframe.
  
  Returns
  -------
      The result of op map stage.
code: def execute_map(
      cls, op, in_data: pd.DataFrame
  ) -> Union[pd.DataFrame, pd.Series]:
      """
      Map stage implement.
  
      Parameters
      -------
      op : Any operand
          DataFrame operand.
      in_data : pd.DataFrame
          Input dataframe.
  
      Returns
      -------
          The result of op map stage.
      """
  
file_path: mars/mars/dataframe/groupby/custom_aggregation.py
imports: from abc import ABC, abstractmethod
  from typing import Dict, Type, Union
  import pandas
label_desc: Use image node_id 1 for calling the DataFrameCustomGroupByAggMixin obj's underlying member method code with example usage: obj.execute_map(cls, op, in_data) without return types