Ads not showing second time

[MacAhsan]

I am using this plugin https://github.com/coop182/jquery.dfp.js in my backbonejs project.
why are we using this block of code. Is it because of performance of google guideline?

// make sure we don't load gpt.js multiple times
                    dfpIsLoaded = dfpIsLoaded || $('script[src*="googletagservices.com/tag/js/gpt.js"]').length;
                    if (dfpIsLoaded) {
                        if (adsCouldNeverBeInitilized) {
                            execBlockEvents();
                        }
                        return $.Deferred().resolve();

                    }