Xamarin.Forms.Labs FileNotFoundException error in xaml

hello!
I'm trying to use ExtendedViewCell control in my listview to hide the separation bar. I added the Xamarin.Forms.Labs (Core) package with nuget. But in my xaml it throws the FileNotFoundException error.

System.IO.FileNotFoundException: Could not load file or assembly 'Xamarin.Forms.Labs' or one of its dependencies. The system cannot find the file specified.

File name: 'Xamarin.Forms.Labs'>

And here is how is defined:

xmlns:local="clr-namespace:SanpruIOS;assembly=SanpruIOS"

xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:controls="clr-namespace:Xamarin.Forms.Labs.Controls;assembly=Xamarin.Forms.Labs">

Do you know where is the problem?