code: def test_strip(self):
      dataframe1 = pd.DataFrame(
          {
              "0": 2 * [np.nan] + list(range(7)) + [np.nan],
              "1": [np.nan] + list(range(7)) + 2 * [np.nan],
          },
          index=self.times1,
      )
      series1 = TimeSeries.from_dataframe(dataframe1)
  
      assert (series1.strip().time_index == self.times1[1:-1]).all()
      assert (
          series1.strip(how="any").time_index == self.times1[2:-2]
      ).all()
  
imports: import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.tests.test_timeseries import TestTimeSeries
label_desc: Use image node_id 13 for calling the TestTimeSeriesMultivariate obj's underlying member method code with example usage: obj.test_strip() without return types