code: def test_cosine_drift():
      # add something so that when the tests are launched from a different directory
      # we still find the file ' 'dctmtx_N_20_order_4.txt' ?
  
      spm_drifts = DMTX[
          "cosbf_dt_1_nt_20_hcut_0p1"
      ]  # np.loadtxt('dctmtx_N_20_order_4.txt')
      tim = np.arange(20)
      P = 10  # period is half the time, gives us an order 4
      nipy_drifts = _cosine_drift(P, tim)  #
      assert_almost_equal(spm_drifts[:, 1:], nipy_drifts[:, :-1])
  
imports: import os.path
  from unittest import skipIf
  import numpy
  from numpy.testing import assert_almost_equal, assert_array_equal
  from ..design_matrix import _convolve_regressors, _cosine_drift, dmtx_from_csv, dmtx_light, make_dmtx
  from ..experimental_paradigm import BlockParadigm, EventRelatedParadigm
label_desc: Use image node_id 6 for calling a global function with example usage: test_cosine_drift() without return types