error CS0246: 未能找到类型或命名空间名“IExample”

vs2017 .NET CORE 2.2

源代码：

using System;
using System.Diagnostics;
using System.Text;
using Tensorflow;
using static Tensorflow.Binding;

namespace TensorFlowNET.Examples
{
    /// <summary>
    /// Simple hello world using TensorFlow
    /// </summary>
    public class HelloWorld : IExample
    {
        public void Run()
        {
            /* Create a Constant op
               The op is added as a node to the default graph.

               The value returned by the constructor represents the output
               of the Constant op. */
            var hello = tf.constant("Hello, TensorFlow!");

            // Start tf session
            using (var sess = tf.Session())
            {
                // Run the op
                var result = sess.run(hello);
                Console.WriteLine(result);
            }
        }
    }
}

报错：error CS0246: 未能找到类型或命名空间名“IExample”(是否缺少 using 指令或程序集引用?)

网上到处都找不到答案

源代码来自https://tensorflownet.readthedocs.io/en/latest/HelloWorld.html