docs: def import_one_to_many(self, file_path, column_index, parent_table, column_in_one2many_table):
          """
          
          :param file_path: 
          :param column_index: 
          :param parent_table:
          :param column_in_one2many_table: 
          """
          chunks = pd.read_table(
              file_path,
              usecols=[column_index],
              header=None,
              comment='#',
              index_col=False,
              chunksize=1000000,
              dtype=self.get_dtypes(parent_table.model)
          )
  
          for chunk in chunks:
              child_values = []
              parent_id_values = []
  
              chunk.dropna(inplace=True)
              chunk.index += 1
  
              for parent_id, values in chunk.iterrows():
                  entry = values[column_index]
                  if not isinstance(entry, str):
                      entry = str(entry)
                  for value in entry.split("|"):
                      parent_id_values.append(parent_id)
                      child_values.append(value.strip())
  
              parent_id_column_name = parent_table.name + '__id'
              o2m_table_name = defaults.TABLE_PREFIX + parent_table.name + '__' + column_in_one2many_table
  
              pd.DataFrame({
                  parent_id_column_name: parent_id_values,
                  column_in_one2many_table: child_values
              }).to_sql(name=o2m_table_name, if_exists='append', con=self.engine, index=False)