code: def init_optimizer(self, kvstore='local', optimizer='sgd',
                         optimizer_params=(('learning_rate', 0.01),),
                         force_init=False):
          
          assert self.binded and self.params_initialized
          if self.optimizer_initialized and not force_init:
              self.logger.warning('optimizer already initialized, ignoring.')
              return
  
          for module in self._modules:
              module.init_optimizer(kvstore=kvstore, optimizer=optimizer,
                                    optimizer_params=optimizer_params, force_init=force_init)
  
          self.optimizer_initialized = True
docs: Installs and initializes optimizers.
  
          Parameters
          ----------
          kvstore : str or KVStore
              Default `'local'`.
          optimizer : str or Optimizer
              Default `'sgd'`
          optimizer_params : dict
              Default ``(('learning_rate', 0.01),)``. The default value is not a dictionary,
              just to avoid pylint warning of dangerous default values.
          force_init : bool
              Default ``False``, indicating whether we should force re-initializing the
              optimizer in the case an optimizer is already installed.