code: def __call__(self, df_features):
      if self.dtype == "bool":
          return df_features.astype(np.int8)
      else:
          return df_features.astype(np.float32)
  
file_path: qlib/qlib/contrib/data/highfreq_processor.py
imports: import os
  import numpy
  import pandas
  from qlib.data.dataset.processor import Processor
  from qlib.data.dataset.utils import fetch_df_by_index
  from typing import Dict
label_desc: Use image node_id 3 for calling the HighFreqTrans obj's underlying member method code with example usage: obj.__call__(df_features) and returns: df_features, df_features