code: def __init__(self, instrument: str, field: str, freq: str, db_region: str = None, **kwargs):  # type: ignore
      super().__init__(
          instrument=instrument,
          field=field,
          freq=freq,
          db_region=db_region,
          **kwargs,
      )
      self.field = field
      calendar = sorted(self.df["datetime"].unique())
      df_calendar = pd.DataFrame(
          calendar, columns=["datetime"]
      ).set_index("datetime")
      df = self.df[self.df["symbol"] == instrument]
      data_dt_field = "datetime"
      cal_df = df_calendar[
          (df_calendar.index >= df[data_dt_field].min())
          & (df_calendar.index <= df[data_dt_field].max())
      ]
      df = df.set_index(data_dt_field)
      df_data = df.reindex(cal_df.index)
      date_index = df_calendar.index.get_loc(df_data.index.min())  # type: ignore
      df_data.reset_index(inplace=True)
      df_data.index += date_index
      self._data = df_data
  
imports: from typing import Union, List, Dict, Tuple
  import unittest
  import pandas
  import numpy
  import io
  from .data import GetData
  from ..None import init
  from ..constant import REG_CN, REG_TW
  from qlib.data.filter import NameDFilter
  from qlib.data import D
  from qlib.data.data import Cal, DatasetD
  from qlib.data.storage import CalendarStorage, InstrumentStorage, FeatureStorage, CalVT, InstKT, InstVT
label_desc: Use image node_id 1 to create a new MockFeatureStorage object from inherited base classes: MockStorageBase, FeatureStorage with example: obj = MockFeatureStorage(instrument, field, freq, db_region)