razor - GlassMapper Render Link add Target for external Links -

we on sitecore 8.1 glassmapper 4.4.1.188.

we rendering image in anchor below:

 using (beginrenderlink(item, x => x.carousellink, iseditable: true))  {      @renderimage(item, x => x.carouselimage, iseditable: true)  }

all works well.

how can force renderlink insert html target attribute based on sitecore input general link?

so, if content editor picks "external link" need link generated target="_blank"

when select external link, use new browser option:

this cshtml code:

@using (html.glass().beginrenderlink(model, x => x.link)) {     <span>aaa</span> }

and html output:

<a href="http://google.com" target="_blank"><span>aaa</span></a>

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