message: fix get dataframe
diff: @@ -59,8 +59,8 @@ class BenchmarkResult:
  return dmp
  def dump(self, filename):
  - if self.data_frame:
  - self.data_frame = None
  + if isinstance(self.__data_frame, pd.DataFrame):
  + self.__data_frame = None
  with open(filename, 'wb') as handle:
  pickle.dump(self, handle, protocol=pickle.HIGHEST_PROTOCOL)
  logging.info("Saved BenchmarkResult to {}".format(
  