code: def test_learning_rate():
      o1 = mx.optimizer.Optimizer(learning_rate=0.01)
      o1.set_learning_rate(0.2)
      assert o1.learning_rate == 0.2
  
      lr_s = lr_scheduler.FactorScheduler(step=1)
      o2 = mx.optimizer.Optimizer(lr_scheduler=lr_s, learning_rate=0.3)
      assert o2.learning_rate == 0.3
      o2.lr_scheduler.base_lr = 0.4
      assert o2.learning_rate == 0.4
  
      lr_s = lr_scheduler.FactorScheduler(step=1, base_lr=1024)
      o3 = mx.optimizer.Optimizer(lr_scheduler=lr_s)
      assert o3.learning_rate == 1024
  
imports: import itertools
  import numpy
  import itertools
  import mxnet
  import mxnet.lr_scheduler
  from mxnet import gluon
  import unittest
  import pytest
  import math
  from mxnet.test_utils import *
  from common import retry, xfail_when_nonstandard_decimal_separator
label_desc: Use image node_id 1 for calling a global function with example usage: test_learning_rate() without return types