code: def test_phase(self):
      f = filterbank(40, 512)
      c = cvec(512)
      c.phas[:] = np.pi
      assert_equal(f(c), 0)
  
imports: import numpy
  from numpy.testing import TestCase, assert_equal, assert_almost_equal
  from aubio import cvec, filterbank, float_type
  from utils import array_from_text_file
label_desc: Use image node_id 3 for calling the aubio_filterbank_test_case obj's underlying member method code with example usage: obj.test_phase() without return types