flight/Engine.php
public function _render($file, $data = null, $key = null) {
        if ($key !== null) {
            $this->view()->set($key, $this->view()->fetch($file, $data));
        }
        else {
            $this->view()->render($file, $data);
        }
    }
public function _render($file, $data = null, $key = null) {
        if ($key !== null) {
            $this->view()->set($key, $this->view()->fetch($file, $data));
        }
        else {
            $this->view()->render($file, $data);
        }
    }
Renders a template.

@param string $file Template file
@param array $data Template data
@param string $key View variable name
@throws \Exception