Constructor.
@api
ParameterBagInterface $parameterBag A ParameterBagInterface instance:
public function __construct(ParameterBagInterface $parameterBag = null) {
$this->parameterBag = null === $parameterBag ? new ParameterBag() : $parameterBag;
$this->services = array();
$this->scopes = array();
$this->scopeChildren = array();
$this->scopedServices = array();
$this->scopeStacks = array();
$this
->set('service_container', $this);
}