public function addServiceDefinitionProvider(ServiceDefinitionProvider $provider) : Capabilities
    {
        if (! isset($this->serviceDefinitionProviders[$provider->handles()])) {

            $this->serviceDefinitionProviders[$provider->handles()] = $provider;
        }

        return $this;
    }
public function addServiceDefinitionProvider(ServiceDefinitionProvider $provider) : Capabilities
    {
        if (! isset($this->serviceDefinitionProviders[$provider->handles()])) {

            $this->serviceDefinitionProviders[$provider->handles()] = $provider;
        }

        return $this;
    }
@param ServiceDefinitionProvider $provider

@return Capabilities