code: def _filling_gaps(res):
      nan_ind = np.argwhere(np.isnan(res))
      res[nan_ind] = -100.0
  
      # Gaps in first and last elements fills with mean value
      if 0 in nan_ind:
          res[0] = np.mean(res)
      if int(len(res) - 1) in nan_ind:
          res[int(len(res) - 1)] = np.mean(res)
  
      # Gaps in center of timeseries fills with linear interpolation
      if len(np.ravel(np.argwhere(np.isnan(res)))) != 0:
          gf = SimpleGapFiller()
          res = gf.linear_interpolation(res)
  
      return res
  
imports: from copy import copy
  from typing import Optional
  import numpy
  from scipy import stats
  from scipy.special import boxcox, inv_boxcox
  from statsmodels.tsa.api import STLForecast
  from statsmodels.tsa.arima.model import ARIMA
  from fedot.core.data.data import InputData, OutputData
  from fedot.core.operations.evaluation.operation_implementations.data_operations.ts_transformations import ts_to_table
  from fedot.core.operations.evaluation.operation_implementations.implementation_interfaces import ModelImplementation
  from fedot.core.operations.operation_parameters import OperationParameters
  from fedot.core.repository.dataset_types import DataTypesEnum
  from fedot.utilities.ts_gapfilling import SimpleGapFiller
label_desc: Use image node_id 9 for calling the ARIMAImplementation obj's underlying member method code with example usage: obj._filling_gaps(res) and returns: res