Error in file SalepriceResolver.php

Problem/Motivation

When my reservation is put on cart, I have this error

Error: Call to undefined method Drupal\commerce_cart\CartManager::getCart() in Drupal\bee\Resolvers\SalepriceResolver->resolve() (line 46 of modules/contrib/bee/src/Resolvers/SalepriceResolver.php). 

On create function we have this

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    $instance->cartProvider = $container->get('commerce_cart.cart_provider');
    return $instance;
  }

But instance is not define.

And why we have this file SalepriceResolver.php closest SalepriceResolver.php.

Thanks