override Adam _finish.

src/TensorFlowNET.Core/Train/AdamOptimizer.cs

@@ -97,6 +97,25 @@ namespace Tensorflow.Train
             }
         }
 
+        public override Operation _finish(Operation[] update_ops, string name_scope)
+        {
+            var operations = new List<ITensorOrOperation>();
+            operations.AddRange(update_ops);
+
+            with(ops.control_dependencies(update_ops), delegate
+            {
+                var (beta1_power, beta2_power) = _get_beta_accumulators();
+                ops.colocate_with(beta1_power);
+                var update_beta1 = beta1_power.assign(beta1_power * _beta1_t, use_locking: _use_locking);
+                var update_beta2 = beta2_power.assign(beta2_power * _beta2_t, use_locking: _use_locking);
+
+                operations.Add(update_beta1);
+                operations.Add(update_beta1);
+            });
+
+            return control_flow_ops.group(operations.ToArray(), name: name_scope);
+        }
+
         private (RefVariable, RefVariable) _get_beta_accumulators()
         {
             ops.init_scope();