code: def test_linear(self, xp, scp, func):
      x = xp.asarray([1, 2, 3, 4, 5, 6, 7])
      return func(x, xp, scp)
  
imports: from math import pi
  import pytest
  import cupy
  import numpy
  from cupy import testing
  from cupy.testing import assert_allclose
  import cupyx.scipy.fft
  import cupyx.scipy.signal
label_desc: Use image node_id 3 for calling the Test1D obj's underlying member method code with example usage: obj.test_linear(xp, scp, func) and returns: func