BlockFactory.php
protected function isContainerBlock($id)
    {
        return $this->typeHelper->isInstanceOf(
            $this->rawLayout->getProperty($id, RawLayout::BLOCK_TYPE, true),
            ContainerType::NAME
        );
    }
protected function isContainerBlock($id)
    {
        return $this->typeHelper->isInstanceOf(
            $this->rawLayout->getProperty($id, RawLayout::BLOCK_TYPE, true),
            ContainerType::NAME
        );
    }
protected function isContainerBlock ( $ id ) { return $ this -> typeHelper -> isInstanceOf ( $ this -> rawLayout -> getProperty ( $ id , RawLayout :: BLOCK_TYPE , true ) , ContainerType :: NAME ) ; }
Checks whether the given block is a container for other blocks

@param string $id

@return bool
Checks whether the given block is a container for other blocks