Replace tf.keras.callbacks.TensorBoard callback with a new callback TensorBoardWithValidation inherited from the former callback, which makes evaluation at the end of specified epochs and export the results to tensorboard.

PiperOrigin-RevId: 219749605

Author: rachellj218

tensorflow/contrib/tpu/python/tpu/keras_support.py

@@ -1536,10 +1536,17 @@ def evaluate(self,
                verbose=1,
                sample_weight=None,
                steps=None):
-    assert not self._numpy_to_infeed_manager_list  # Ensure empty.
+    original_numpy_to_infeed_manager_list = []
+    if self._numpy_to_infeed_manager_list:
+      # evaluate call may be executed as callbacks during the training. In this
+      # case, _numpy_to_infeed_manager_list is not empty, so save it for
+      # recovery at the end of evaluate call.
+      original_numpy_to_infeed_manager_list = self._numpy_to_infeed_manager_list
+      self._numpy_to_infeed_manager_list = []
 
     with _tpu_session_context():
-      infeed_managers = []  # Managers to clean up at the end of the fit call.
+      # Managers to clean up at the end of the evaluate call.
+      infeed_managers = []
       if isinstance(x, dataset_ops.Dataset):
         # TODO(b/111413240): Support taking a tf.data.Dataset directly.
         raise ValueError(
@@ -1569,7 +1576,8 @@ def evaluate(self,
         return super(KerasTPUModel, self).evaluate(x, y, batch_size, verbose,
                                                    sample_weight, steps)
       finally:
-        self._numpy_to_infeed_manager_list = []
+        self._numpy_to_infeed_manager_list = (
+            original_numpy_to_infeed_manager_list)
 
   def _pipeline_fit(self, x, y, batch_size, epochs, verbose, callbacks,
                     validation_split, validation_data, shuffle, class_weight,