code: def fit(
      self,
      series: TimeSeries,
      future_covariates: Optional[TimeSeries] = None,
  ):
      # for VARIMA we need to process target `series` before calling
      # TransferableFutureCovariatesLocalForecastingModel's fit() method
      self._last_values = (
          series.last_values()
      )  # needed for back-transformation when d=1
  
      series = self._differentiate_series(series)
  
      super().fit(series, future_covariates)
  
      return self
  
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 3 for calling the VARIMA obj's underlying member method code with example usage: obj.fit(series, future_covariates) and returns: self