Make data and evaluation visualization optional.

Summary:
Make data and evaluation visualization optional.
* could return None.

Reviewed By: zhanghang1989, wat3rBro

Differential Revision: D27316632

fbshipit-source-id: 2a85db4815cbf3407a20a74c125dcd52d75167fa

d2go/runner/default_runner.py

@@ -8,7 +8,7 @@ import math
 import os
 from collections import OrderedDict
 from functools import lru_cache, partial
-from typing import Type
+from typing import Type, Optional
 
 import d2go.utils.abnormal_checker as abnormal_checker
 import detectron2.utils.comm as comm
@@ -317,16 +317,18 @@ class Detectron2GoRunner(BaseRunner):
                 tbx_writer = _get_tbx_writer(get_tensorboard_log_dir(cfg.OUTPUT_DIR))
                 logger.info("Adding visualization evaluator ...")
                 mapper = self.get_mapper(cfg, is_train=False)
-                evaluator._evaluators.append(
-                    self.get_visualization_evaluator()(
-                        cfg,
-                        tbx_writer,
-                        mapper,
-                        dataset_name,
-                        train_iter=train_iter,
-                        tag_postfix=model_tag,
+                vis_eval_type = self.get_visualization_evaluator()
+                if vis_eval_type is not None:
+                    evaluator._evaluators.append(
+                        vis_eval_type(
+                            cfg,
+                            tbx_writer,
+                            mapper,
+                            dataset_name,
+                            train_iter=train_iter,
+                            tag_postfix=model_tag,
+                        )
                     )
-                )
 
             results_per_dataset = inference_on_dataset(model, data_loader, evaluator)
 
@@ -485,14 +487,14 @@ class Detectron2GoRunner(BaseRunner):
         data_loader = build_d2go_train_loader(cfg, mapper)
 
         if comm.is_main_process():
-            tbx_writer = _get_tbx_writer(get_tensorboard_log_dir(cfg.OUTPUT_DIR))
-            data_loader = cls.get_data_loader_vis_wrapper()(
-                cfg, tbx_writer, data_loader
-            )
+            data_loader_type = cls.get_data_loader_vis_wrapper()
+            if data_loader_type is not None:
+                tbx_writer = _get_tbx_writer(get_tensorboard_log_dir(cfg.OUTPUT_DIR))
+                data_loader = data_loader_type(cfg, tbx_writer, data_loader)
         return data_loader
 
     @staticmethod
-    def get_data_loader_vis_wrapper() -> Type[DataLoaderVisWrapper]:
+    def get_data_loader_vis_wrapper() -> Optional[Type[DataLoaderVisWrapper]]:
         return DataLoaderVisWrapper
 
     @staticmethod
@@ -524,7 +526,7 @@ class Detectron2GoRunner(BaseRunner):
         return mapper
 
     @staticmethod
-    def get_visualization_evaluator() -> Type[VisualizationEvaluator]:
+    def get_visualization_evaluator() -> Optional[Type[VisualizationEvaluator]]:
         return VisualizationEvaluator
 
     @staticmethod