code: def test_first_last_values(self):
      assert self.series1.first_values().tolist() == [0, 5, 10]
      assert self.series3.last_values().tolist() == [10, 20]
      assert self.series1.univariate_component(
          1
      ).first_values().tolist() == [5]
      assert self.series3.univariate_component(
          1
      ).last_values().tolist() == [20]
  
imports: import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.tests.test_timeseries import TestTimeSeries
label_desc: Use image node_id 19 for calling the TestTimeSeriesMultivariate obj's underlying member method code with example usage: obj.test_first_last_values() without return types