如下代码使用resharper的反编译器反编译的asp.net core的代码，没有方法实现，有的又有，请问下是怎么回事呢

// Decompiled with JetBrains decompiler
// Type: Microsoft.Extensions.Hosting.GenericHostWebHostBuilderExtensions
// Assembly: Microsoft.AspNetCore.Hosting, Version=3.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60
// MVID: 1BCE6D72-7E5F-4A20-AD29-79535E6D1346
// Assembly location: C:\Program Files\dotnet\packs\Microsoft.AspNetCore.App.Ref\3.1.3\ref\netcoreapp3.1\Microsoft.AspNetCore.Hosting.dll

using Microsoft.AspNetCore.Hosting;
using System;

namespace Microsoft.Extensions.Hosting
{
  public static class GenericHostWebHostBuilderExtensions
  {
    public static IHostBuilder ConfigureWebHost(
      this IHostBuilder builder,
      Action<IWebHostBuilder> configure);
  }
}