code: def calc_stat_values(self):
      self._std = self._dataset.groupby(DT_COL_NAME).std()
      self._mean = self._dataset.groupby(DT_COL_NAME).mean()
  
imports: import pandas
  import numpy
  from qlib.contrib.report.data.base import FeaAnalyser
  from qlib.contrib.report.utils import sub_fig_generator
  from qlib.utils.paral import datetime_groupby_apply
  from qlib.contrib.eva.alpha import pred_autocorr_all
  from loguru import logger
  import seaborn
label_desc: Use image node_id 1 for calling the FeaMeanStd obj's underlying member method code with example usage: obj.calc_stat_values() without return types