code: def test_unknown_method(self):
      method = "foo"
      f0 = 10.0
      f1 = 20.0
      t1 = 1.0
      t = np.linspace(0, t1, 10)
      assert_raises(ValueError, waveforms.chirp, t, f0, t1, f1, method)
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  from numpy.testing import assert_almost_equal, assert_equal, assert_, assert_allclose, assert_array_equal
  from pytest import raises
  import scipy.signal.waveforms
label_desc: Use image node_id 15 for calling the TestChirp obj's underlying member method code with example usage: obj.test_unknown_method() without return types