doGetParent example

    public function getParent(array $context)
    {
        if (null !== $this->parent) {
            return $this->parent;
        }

        try {
            $parent = $this->doGetParent($context);

            if (false === $parent) {
                return false;
            }

            if ($parent instanceof self || $parent instanceof TemplateWrapper) {
                return $this->parents[$parent->getSourceContext()->getName()] = $parent;
            }

            if (!isset($this->parents[$parent])) {
                $this->parents[$parent] = $this->loadTemplate($parent);
            }