code: def register(klass):
          
          assert(isinstance(klass, type))
          name = klass.__name__.lower()
          if name in Optimizer.opt_registry:
              warnings.warn('WARNING: New optimizer %s.%s is overriding '
                            'existing optimizer %s.%s' %
                            (klass.__module__, klass.__name__,
                             Optimizer.opt_registry[name].__module__,
                             Optimizer.opt_registry[name].__name__))
          Optimizer.opt_registry[name] = klass
          return klass
docs: Registers a new optimizer.
  
          Once an optimizer is registered, we can create an instance of this
          optimizer with `create_optimizer` later.
  
          Examples
          --------
  
          >>> @mx.optimizer.Optimizer.register
          ... class MyOptimizer(mx.optimizer.Optimizer):
          ...     pass
          >>> optim = mx.optimizer.Optimizer.create_optimizer('MyOptimizer')
          >>> print(type(optim))
          <class '__main__.MyOptimizer'>