code: def test_const_decay_scheduler(self, dev):
      c1 = opt.Constant(0.2)
      step = tensor.Tensor((1,), device=dev).set_value(0)
      lr_val = c1(step)
      np.testing.assert_array_almost_equal(
          tensor.to_numpy(c1(step)), [0.2]
      )
      step += 1
      np.testing.assert_array_almost_equal(
          tensor.to_numpy(c1(step)), [0.2]
      )
  
imports: from __future__ import division
  import math
  import unittest
  import numpy
  import functools
  from singa import tensor
  from singa import singa_wrap
  from singa import opt
  from cuda_helper import gpu_dev, cpu_dev
label_desc: Use image node_id 3 for calling the TestDecayScheduler obj's underlying member method code with example usage: obj.test_const_decay_scheduler(dev) without return types