code: def _invert_transformation(self, series_df: pd.DataFrame):
      if self.d == 0:
          return series_df
      if self._last_num_samples > 1:
          series_df = np.tile(
              self._last_values, (self._last_num_samples, 1)
          ).T + series_df.cumsum(axis=0)
      else:
          series_df = self._last_values + series_df.cumsum(axis=0)
      return series_df
  
file_path: darts/darts/models/forecasting/varima.py
imports: from typing import Optional
  import numpy
  import pandas
  from statsmodels.tsa.api import VARMAX
  from darts.logging import get_logger, raise_if
  from darts.models.forecasting.forecasting_model import TransferableFutureCovariatesLocalForecastingModel
  from darts.timeseries import TimeSeries
label_desc: Use image node_id 6 for calling the VARIMA obj's underlying member method code with example usage: obj._invert_transformation(series_df) and returns: series_df, series_df