Convenience to string method.

def device_product_str(self, indent):
        """Convenience to string method.
        """
        s = "Vendor: {}\n".format(self.vendor)
        s += indent + "Product: {}\n".format((self.product and product_map[self.product]) or "Unknown")
        s += indent + "Version: {}\n".format(self.version)
        return s