code: def test_spread(self):
      o = specdesc("spread")
      c = cvec(1024)
      ramp = arange(c.length, dtype=float_type)
      assert_equal(0.0, o(c))
  
      a = ramp
      c.norm = a
      centroid = sum(a * a) / sum(a)
      spread = sum(a * pow(ramp - centroid, 2.0)) / sum(a)
      assert_almost_equal(o(c), spread, decimal=1)
  
imports: from numpy.testing import TestCase, assert_equal, assert_almost_equal
  from numpy import random, arange, log, zeros
  from aubio import specdesc, cvec, float_type
label_desc: Use image node_id 10 for calling the aubio_specdesc obj's underlying member method code with example usage: obj.test_spread() without return types