class_docstr: Implements stochastic gradient descent (optionally with momentum).
  
  Nesterov momentum is based on the formula from `On the importance of initialization and momentum in deep learning`__.
  
  Args:
      lr(float): learning rate
      momentum(float, optional): momentum factor(default: 0)
      weight_decay(float, optional): weight decay(L2 penalty)(default: 0)
      dampening(float, optional): dampening for momentum(default: 0)
      nesterov(bool, optional): enables Nesterov momentum(default: False)
  
  Typical usage example:
      >> > from singa import opt
      >> > optimizer = opt.SGD(lr=0.1, momentum=0.9)
      >> > optimizer.update()
  
  __ http: // www.cs.toronto.edu / %7Ehinton / absps / momentum.pdf
  
  .. note::
      The implementation of SGD with Momentum / Nesterov subtly differs from
      Sutskever et. al. and implementations in some other frameworks.
  
      Considering the specific case of Momentum, the update can be written as
  
      .. math::
                v = 
  ho * v + g \
                p = p - lr * v
  
      where p, g, v and: math: `
  ho` denote the parameters, gradient,
      velocity, and momentum respectively.
  
      This is in contrast to Sutskever et. al. and
      other frameworks which employ an update of the form
  
      .. math::
           v = 
  ho * v + lr * g \
           p = p - v
  
      The Nesterov version is analogously modified.
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code: def __init__(
      self,
      lr=0.1,
      momentum=0,
      dampening=0,
      weight_decay=0,
      nesterov=False,
      dtype=tensor.float32,
  ):
      super(MSSGD, self).__init__(lr)
  
      # init momentum
      if type(momentum) == float or type(momentum) == int:
          if momentum < 0.0:
              raise ValueError(
                  "Invalid momentum value: {}".format(momentum)
              )
          self.momentum = Constant(momentum)
      elif isinstance(momentum, DecayScheduler):
          self.momentum = momentum
          momentum = momentum.init_value
      else:
          raise TypeError("Wrong momentum type")
      # self.dtype = dtype
      # self.mom_value = self.momentum(self.step_counter).as_type(self.dtype)
      self.mom_value = self.momentum(self.step_counter)
  
      # init dampening
      if type(dampening) == float or type(dampening) == int:
          self.dampening = Constant(dampening)
      elif isinstance(dampening, DecayScheduler):
          self.dampening = dampening
          dampening = dampening.init_value
      else:
          raise TypeError("Wrong dampening type")
      # self.dam_value = self.dampening(self.step_counter).as_type(self.dtype)
      self.dam_value = self.dampening(self.step_counter)
  
      # init weight_decay
      if type(weight_decay) == float or type(weight_decay) == int:
          if weight_decay < 0.0:
              raise ValueError(
                  "Invalid weight_decay value: {}".format(weight_decay)
              )
          self.weight_decay = Constant(weight_decay)
      elif isinstance(weight_decay, DecayScheduler):
          self.weight_decay = weight_decay
      else:
          raise TypeError("Wrong weight_decay type")
      # self.decay_value = self.weight_decay(self.step_counter).as_type(self.dtype)
      self.decay_value = self.weight_decay(self.step_counter)
  
      # init other params
      self.nesterov = nesterov
      self.moments = dict()
  
      # check value
      if nesterov and (momentum <= 0 or dampening != 0):
          raise ValueError(
              "Nesterov momentum requires a momentum and zero dampening"
          )
  
imports: import time
  from src.tools import utils
  from singa import singa_wrap
  from singa import device
  from singa import tensor
  from singa import opt
  from singa import autograd
  from singa.opt import Optimizer
  from singa.opt import DecayScheduler
  from singa.opt import Constant
  import numpy
  import time
  import argparse
  from PIL import Image
  from torch.utils.data import DataLoader
label_desc: Use image node_id 1 to create a new MSSGD object from inherited base classes: MSOptimizer with example: obj = MSSGD(lr, momentum, dampening, weight_decay, nesterov, dtype)