docstr: Check that values are properly extracted when the beginning of the series is aligned with the low frequency
  anchor value (day of the week).
docstr_tok: ["Check","that","values","are","properly","extracted","when","the","beginning","of","the","series","is","aligned","with","the","low","frequency","anchor","value","(","day","of","the","week",")","."]
code: def test_aligned_low_freq_anchor(self):
      """
      Check that values are properly extracted when the beginning of the series is aligned with the low frequency
      anchor value (day of the week).
      """
      ts = linear_timeseries(
          start=pd.Timestamp("2000-01-01"),
          freq="D",
          start_value=1,
          end_value=22,
          length=22,
      )
      assert ts.time_index[0].day_name() == "Saturday"
  
      midas_sat = MIDAS(low_freq="W-SAT", strip=False)
      ts_saturday_anchor = midas_sat.fit_transform(ts)
      # the resampled series start at the same timestamp because `strip=False`
      assert ts_saturday_anchor.start_time() == ts.start_time()
      assert ts_saturday_anchor.end_time() == ts.end_time()
  
      # padding in the first row
      first_row_exp = np.empty(6)
      first_row_exp.fill(np.nan)
      first_row_exp = np.concatenate(
          [first_row_exp, ts[0].values().flatten()]
      )
      np.testing.assert_array_equal(
          ts_saturday_anchor[0].values().flatten(), first_row_exp
      )
  
      # last row should be completely filled
      np.testing.assert_array_equal(
          ts_saturday_anchor[-1].values().flatten(),
          ts[-7:].values().flatten(),
      )
  
      # inverse transform
      ts_inv_saturday_anchor = midas_sat.inverse_transform(
          ts_saturday_anchor
      )
      np.testing.assert_array_equal(
          ts.values(), ts_inv_saturday_anchor.values()
      )
      assert ts.time_index.equals(ts_inv_saturday_anchor.time_index)
  
imports: import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.dataprocessing.transformers import MIDAS
  from darts.models import LinearRegressionModel
  from darts.utils.timeseries_generation import generate_index, linear_timeseries
label_desc: Use image node_id 15 for calling the TestMIDAS obj's underlying member method code with example usage: obj.test_aligned_low_freq_anchor() without return types