* Describes the interface of a container that exposes methods to read its entries.
interface ContainerInterface
* Finds an entry of the container by its identifier and returns it.
* @param string $id Identifier of the entry to look for.
* @throws NotFoundExceptionInterface No entry was found for **this** identifier.
* @throws ContainerExceptionInterface Error while retrieving the entry.
public function get($id);
* Returns true if the container can return an entry for the given identifier.
* Returns false otherwise.
* `has($id)` returning true does not mean that `get($id)` will not throw an exception.
* It does however mean that `get($id)` will not throw a `NotFoundExceptionInterface`.
* @param string $id Identifier of the entry to look for.
public function has($id);