code: protected function registerProviders()
  	{
  		$dependants = [];
  
  		foreach ($this->providers as $provider) {
  			if (is_string($provider)) {
  				$provider = new $provider();
  			}
  
  			$this->registerProvider($provider);
  
  			if ($provider instanceof DependantProviderInterface) {
  				$dependants[] = $provider;
  			}
  		}
  
  		foreach ($dependants as $dependant) {
  			$this->checkProviderDependencies($dependant);
  		}
  	}
docs: Register all of the application's service providers.
  
  @return void