问如何动态了解和实例化Python模块中实现的一个类

EN

from generic_data_writer import GenericDataWriter

class ExcelDataWriter(GenericDataWriter):
   def __init__(self, config):
       super().__init__(config)
       self.sheet_name = config.get('sheetname')

   def write_data(self, pandas_dataframe):
       pandas_dataframe.to_excel(
           self.get_output_file_path_and_name(), # implemented in GenericDataWriter
           sheet_name=self.sheet_name,
           index=self.index)

from generic_data_writer import GenericDataWriter

class CSVDataWriter(GenericDataWriter):
   def __init__(self, config):
       super().__init__(config)
       self.delimiter = config.get('delimiter')
       self.encoding = config.get('encoding')

   def write_data(self, pandas_dataframe):
       pandas_dataframe.to_csv(
           self.get_output_file_path_and_name(), # implemented in GenericDataWriter
           sep=self.delimiter,
           encoding=self.encoding,
           index=self.index)

import os

class GenericDataWriter:
   def __init__(self, config):
       self.output_folder = config.get('output_folder')
       self.output_file_name = config.get('output_file')
       self.output_file_path_and_name = os.path.join(self.output_folder, self.output_file_name)
       self.index = config.get('include_index') # whether to include index column from Pandas' dataframe in the output file

{
"__comment__": "Here, user can provide the path and python file name of the custom data writer module she wants to use."
"custom_data_writer_module": "./data_writers/excel_data_writer.py"

"there_are_more_key_value_pairs_in_this_JSON_config_file": "for other input parameters"
}

import os
import importlib

def main():
    # Do other things to read and process data

    data_writer_class_file = config.get('custom_data_writer_module')
    data_writer_module = importlib.import_module\
            (os.path.splitext(os.path.split(data_writer_class_file)[1])[0])

    dw = data_writer_module.what_should_this_be?   # <=== Here, what should I do to instantiate the right specific data writer (Excel or CSV) class instance?
    for df in dataframes_to_write_to_output_file:
        dw.write_data(df)

if __name__ == "__main__":
    main()