code: def calc_stat_values(self):
      self._skew = datetime_groupby_apply(self._dataset, "skew")
      self._kurt = datetime_groupby_apply(
          self._dataset, pd.DataFrame.kurt
      )
  
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 FeaSkewTurt obj's underlying member method code with example usage: obj.calc_stat_values() without return types