Fix reduce_sum test case

Author: mishun

test/TensorFlowNET.Graph.UnitTest/GradientTest/GradientTest.cs

@@ -185,24 +185,24 @@ import tensorflow.compat.v1 as tf
             x = tf.placeholder(tf.float64, shape = (1, 1))
             m = tf.broadcast_to(x, (2, 3))
             g0 = tf.gradients(tf.reduce_sum(m), x)[0]
-            g1 = tf.gradients(tf.reduce_sum(m, axis = 0), x)[0]
-            g2 = tf.gradients(tf.reduce_sum(m, axis = 1), x)[0]
+            g1 = tf.gradients(tf.reduce_sum(m, axis = 0)[0], x)[0]
+            g2 = tf.gradients(tf.reduce_sum(m, axis = 1)[0], x)[0]
             with tf.compat.v1.Session() as sess:
                 (r0, r1, r2) = sess.run((g0, g1, g2), {x: [[1.0]]})
             */
 
             var x = tf.placeholder(tf.float64, shape: new Shape(1, 1));
             var m = tf.broadcast_to(x, new Shape(2, 3));
             var g0 = tf.gradients(tf.reduce_sum(m), x)[0];
-            var g1 = tf.gradients(tf.reduce_sum(m, axis: 0), x)[0];
-            var g2 = tf.gradients(tf.reduce_sum(m, axis: 1), x)[0];
+            var g1 = tf.gradients(tf.reduce_sum(m, axis: 0)[0], x)[0];
+            var g2 = tf.gradients(tf.reduce_sum(m, axis: 1)[0], x)[0];
 
             using (var session = tf.Session())
             {
                 var (r0, r1, r2) = session.run((g0, g1, g2), new FeedItem(x, new[,] { { 1.0 } }));
                 self.assertFloat64Equal(6.0, r0[0], $"tf.reduce_sum(...)");
-                self.assertFloat64Equal(6.0, r1[0], $"tf.reduce_sum(..., axis = 0)");
-                self.assertFloat64Equal(6.0, r2[0], $"tf.reduce_sum(..., axis = 1)");
+                self.assertFloat64Equal(2.0, r1[0], $"tf.reduce_sum(..., axis = 0)");
+                self.assertFloat64Equal(3.0, r2[0], $"tf.reduce_sum(..., axis = 1)");
             }
         }