code: def test_generate_RW():
      t = np.arange(0.0, 1e2)
      tau = 300
      z = 2.0
      rng = np.random.RandomState(0)
      xmean = rng.rand(1) * 200 - 100
      N = len(t)
      y = generate_damped_RW(
          t, tau=tau, z=z, xmean=xmean, random_state=rng
      )
  
      assert_(len(generate_damped_RW(t)) == N)
      assert_almost_equal(np.mean(y), xmean, 0)
  
imports: import pytest
  import numpy
  from numpy.testing import assert_, assert_almost_equal
  from astroML.time_series import generate_power_law, generate_damped_RW
label_desc: Use image node_id 2 for calling a global function with example usage: test_generate_RW() without return types