code: func NewDeliverService(conf *Config) (DeliverService, error) {
  	ds := &deliverServiceImpl{
  		conf:           conf,
  		blockProviders: make(map[string]blocksprovider.BlocksProvider),
  	}
  	if err := ds.validateConfiguration(); err != nil {
  		return nil, err
  	}
  	return ds, nil
  }
docs: // NewDeliverService construction function to create and initialize
  // delivery service instance. It tries to establish connection to
  // the specified in the configuration ordering service, in case it
  // fails to dial to it, return nil