Wrapper for TagAs did not work (#1462)

* API Overhaul

First draft of the API overhauls changes. Adds most core functionality, including
defining workflow graphs with a ColumnGroup class, the workflow and dataset changes
, most operators converted to use the new api, etc.

* remove debug print statement

* Fix test_io unittest

Also partially fix some tests inside test_workflow

* Handle multi-column joint/combo categorify

* Update JoinGroupby

* Fix differencelag

* add dependencies method (#498)

* Convert TargetEncoding op

* Update nvtabular/workflow.py

Co-authored-by: Richard (Rick) Zamora <rzamora217@gmail.com>

* Update nvtabular/workflow.py

Co-authored-by: Richard (Rick) Zamora <rzamora217@gmail.com>

* Remove workflow code from dataloaders

We should be doing online transforms like
```KerasSequenceLoader(workflow.transform(dataset), ...```  instead of
```KerasSequenceLoader(dataset, workflows=[workflow], ...``` now

* Unittest ops + bugfix in Bucketize (#496)

* test_minmix

* updates test

* unittest ops

* First draft get_embedding_sizes support

Re-add get_embedding_sizes . Note that this changes how we support multi-hot columns here
(sizes are returned same as single hot, and we don't use this method to distinguish between
multi and singlehot columns)

* isort

* Remove groupbystatistics

* implement serialization of statistics

add save_stats/load_stats/clear_stats methods to the workflow, with each statoperator getting
called as appropiate

* Fix TF dataloader unittests

* test_torch_dataloader fixes

* doc strings

* fix tagas

Co-authored-by: Ben Frederickson <github@benfrederickson.com>
Co-authored-by: rnyak <ronayak@hotmail.com>
Co-authored-by: Richard (Rick) Zamora <rzamora217@gmail.com>
Co-authored-by: root <root@dgx06.aselab.nvidia.com>
Co-authored-by: Karl Higley <kmhigley@gmail.com>

nvtabular/ops/add_metadata.py

@@ -53,25 +53,21 @@ def __init__(self, properties=None):
 
 
 # Wrappers for common features
-class TagAsUserID(Operator):
-    @property
-    def output_tags(self):
-        return [Tags.USER_ID]
+class TagAsUserID(AddTags):
+    def __init__(self, tags=None):
+        super().__init__(tags=[Tags.USER_ID, Tags.USER])
 
 
-class TagAsItemID(Operator):
-    @property
-    def output_tags(self):
-        return [Tags.ITEM_ID]
+class TagAsItemID(AddTags):
+    def __init__(self, tags=None):
+        super().__init__(tags=[Tags.ITEM_ID, Tags.ITEM])
 
 
-class TagAsUserFeatures(Operator):
-    @property
-    def output_tags(self):
-        return [Tags.USER]
+class TagAsUserFeatures(AddTags):
+    def __init__(self, tags=None):
+        super().__init__(tags=[Tags.USER])
 
 
-class TagAsItemFeatures(Operator):
-    @property
-    def output_tags(self):
-        return [Tags.ITEM]
+class TagAsItemFeatures(AddTags):
+    def __init__(self, tags=None):
+        super().__init__(tags=[Tags.ITEM])