Migrate to Hydra 1.0

Summary:
- Migrated to Hydra 1.0
- We need to figure out what the best hierarchy is for Classy given Hydra's new capabilities since the original decision might not be the best now
  - I tried out package directives as well and they work well
  - Leaving this for the future though

Documenting the API changes here -
```
pip install .
pip install hydra-core==1.0.0rc1 # to be replaced with final version
classy_project my_hydra_project

# some example runs with the new API
# note that since task, optimizer and param_scheduler are used in args.yaml, they will not need a + prefix in the command

./my_hydra_project/classy_train.py +model=resnet_50
./my_hydra_project/classy_train.py +loss=cross_entropy +model=resnet50
```

Differential Revision: D21916837

fbshipit-source-id: 536d158fc919128998d126d614f57fbe61ef49b9

classy_train.py

@@ -63,6 +63,7 @@
 
 try:
     import hydra
+    import omegaconf
 
     hydra_available = True
 except ImportError:
@@ -154,11 +155,11 @@ def configure_hooks(args, config):
 
 if hydra_available:
 
-    @hydra.main(config_path="hydra_configs/args.yaml")
+    @hydra.main(config_name="hydra_configs/args")
     def hydra_main(cfg):
         args = cfg
         check_generic_args(cfg)
-        config = cfg.config.to_container()
+        config = omegaconf.OmegaConf.to_container(cfg.config)
         main(args, config)
 
 

classy_vision/hydra/conf/config/resnet50_synthetic.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   name: classification_task
   num_epochs: 2

classy_vision/hydra/conf/dataset/synthetic_image.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   dataset:
     train:

classy_vision/hydra/conf/loss/cross_entropy.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   loss:
     name: CrossEntropyLoss

classy_vision/hydra/conf/loss/label_smoothing_cross_entropy.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   loss:
     name: label_smoothing_cross_entropy

classy_vision/hydra/conf/meters/accuracy.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   meters:
     accuracy:

classy_vision/hydra/conf/model/resnet_50.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   model:
     name: resnet

classy_vision/hydra/conf/optimizer/sgd.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   optimizer:
     name: sgd

classy_vision/hydra/conf/param_scheduler/step.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   optimizer:
     param_schedulers:

classy_vision/hydra/conf/task/classification_task.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 config:
   name: classification_task
   num_epochs: 2

classy_vision/templates/synthetic/hydra_configs/args.yaml

@@ -1,3 +1,4 @@
+# @package _global_
 debug: False
 device: null
 checkpoint_folder: ""

hydra_plugins/classy_vision_path/classy_vision_path.py

@@ -4,9 +4,12 @@
 # This source code is licensed under the MIT license found in the
 # LICENSE file in the root directory of this source tree.
 
-from hydra.plugins import SearchPathPlugin
+from hydra.core.config_search_path import ConfigSearchPath
+from hydra.plugins.search_path_plugin import SearchPathPlugin
 
 
 class ClassyVisionPathPlugin(SearchPathPlugin):
-    def manipulate_search_path(self, search_path):
-        search_path.append("classy_vision", "pkg://classy_vision.hydra.conf")
+    def manipulate_search_path(self, search_path: ConfigSearchPath) -> None:
+        search_path.append(
+            provider="classy_vision", path="pkg://classy_vision.hydra.conf"
+        )