How to remove a users manager in AzureAD using Microsoft.Azure.ActiveDirectory.GraphClient

I managed to clear the "manager" field using the code below. It is not using the Microsoft.Azure.ActiveDirectory.GraphClient library but gets the job done.

var token = <get your adal token here>
var httpClient = new HttpClient();
httpClient.DefaultRequestHeaders.Authorization = 
    new AuthenticationHeaderValue("Bearer", token);

var url = "https://graph.windows.net/<tenant domain>/users/<userid>/$links/manager?api-version=1.6"
var resp = httpClient.DeleteAsync(url).Result;
if (!resp.IsSuccessStatusCode)
{
    // log / throw exception etc.   
}