code: def test_low_memory_fit():
      endog = dta["infl"].iloc[:20]
      mod = sarimax.SARIMAX(
          endog, order=(1, 0, 0), concentrate_scale=True
      )
      mod.ssm.set_conserve_memory(MEMORY_NO_GAIN)
  
      res = mod.fit(low_memory=True, disp=False)
      assert_equal(res.filter_results.conserve_memory, MEMORY_CONSERVE)
      assert_(res.llf_obs is None)
      assert_equal(mod.ssm.conserve_memory, MEMORY_NO_GAIN)
  
file_path: statsmodels/statsmodels/tsa/statespace/tests/test_conserve_memory.py
imports: import numpy
  import pandas
  import pytest
  from numpy.testing import assert_equal, assert_allclose, assert_
  from statsmodels.datasets import macrodata
  from statsmodels.tsa.statespace import sarimax, varmax, dynamic_factor
  from statsmodels.tsa.statespace.kalman_filter import MEMORY_NO_FORECAST_MEAN, MEMORY_NO_FORECAST_COV, MEMORY_NO_PREDICTED_MEAN, MEMORY_NO_PREDICTED_COV, MEMORY_NO_PREDICTED, MEMORY_NO_SMOOTHING, MEMORY_NO_GAIN, MEMORY_CONSERVE
label_desc: Use image node_id 7 for calling a global function with example usage: test_low_memory_fit() without return types