class_docstr: python reference implemenation of sgd
code: def __init__(self, learning_rate=0.1, momentum=0.0, **kwargs):
      super(PySparseSGD, self).__init__(
          learning_rate=learning_rate, **kwargs
      )
      self.momentum = momentum
  
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 to create a new PySparseSGD object from inherited base classes: mx.optimizer with example: obj = PySparseSGD(learning_rate, momentum)