code: def gap_time_series_several_first_last_enough_length():
      """Some first and last elements are gaps but not the first and last one"""
      ts = [
          0,
          -100.0,
          -100.0,
          3,
          4,
          5,
          6,
          7,
          8,
          9,
          10,
          11,
          12,
          13,
          14,
          15,
          16,
          17,
          -100.0,
          -100.0,
          20,
      ]
      return np.array(ts, dtype=float)
  
imports: import numpy
  import pytest
  from sklearn.metrics import mean_squared_error
  from typing import Callable
  from examples.simple.time_series_forecasting.gapfilling import get_array_with_gaps
  from fedot.utilities.ts_gapfilling import ModelGapFiller, SimpleGapFiller
  from test.unit.tasks.test_forecasting import get_simple_ts_pipeline
label_desc: Use image node_id 7 for calling a global function with example usage: gap_time_series_several_first_last_enough_length() and returns: np