code: def _data(self):
      df = self._raw_data
      df["key"] = self._generate_row_keys(df)
      df["created_at"] = datetime.utcnow()
      df["feature_data"] = df[self._values]
      df.drop(self._values, inplace=True, axis=1)
      df.drop(self.key, inplace=True, axis=1)
      return df
  
file_path: lore/lore/features/db.py
imports: from abc import ABCMeta
  from datetime import datetime
  import lore.io
  from lore.features.base import BaseFeatureExporter, BaseFeatureImporter
  import lore.metadata
  from lore.metadata import FeatureMetaData
  from sqlalchemy.orm import sessionmaker, scoped_session
  import pandas
  from lore.util import convert_df_columns_to_json
  import json
label_desc: Use image node_id 2 for calling the DBFeatureExporter obj's underlying member method code with example usage: obj._data() and returns: df