public function find($file)
    {
        $found = false;
        $expanded = $this->_expandPrefix($file);
        if (file_exists($expanded)) {
            return $expanded;
        }
        foreach ($this->_paths as $path) {
            $file = $this->_normalizePath($file, DIRECTORY_SEPARATOR);
            $fullPath = $path . $file;

            if (file_exists($fullPath)) {
                $found = $fullPath;
                break;
            }
        }
        return $found;
    }