code: def test_univariate_component(self):
      with pytest.raises(IndexError):
          self.series1.univariate_component(-5)
      with pytest.raises(IndexError):
          self.series1.univariate_component(3)
      seriesA = self.series1.univariate_component(1)
      assert seriesA == TimeSeries.from_times_and_values(
          self.times1, range(5, 15), columns=["1"]
      )
      seriesB = (
          self.series1.univariate_component(0)
          .stack(seriesA)
          .stack(self.series1.univariate_component(2))
      )
      assert self.series1 == seriesB
  
imports: import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.tests.test_timeseries import TestTimeSeries
label_desc: Use image node_id 15 for calling the TestTimeSeriesMultivariate obj's underlying member method code with example usage: obj.test_univariate_component() without return types