We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
[Bug] MISSING for Object Conf cls argument
# 🐛 Bug

OmegaConf cls argument should not be a mandatory value if target is defined. Can we change this to be an optional value with None being the default?
 
** Stack trace/error message **
```
omegaconf.errors.MissingMandatoryValue: Missing mandatory value: scheduler.cls
        full_key: scheduler.cls
        reference_type=ObjectConf
        object_type=ObjectConf
```


## System information
- **Hydra Version** :  1.0.0rc2
- **Python version** : 3.7.7


--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `hydra/types.py`
Content:
```
1 # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
2 from dataclasses import dataclass, field
3 from enum import Enum
4 from typing import Any, Callable, Dict
5 
6 from omegaconf import MISSING
7 
8 TaskFunction = Callable[[Any], Any]
9 
10 
11 @dataclass
12 # This extends Dict[str, Any] to allow for the deprecated "class" field.
13 # Once support for class field removed this can stop extending Dict.
14 class ObjectConf(Dict[str, Any]):
15     # class, class method or function name
16     target: str = MISSING
17 
18     # parameters to pass to cls when calling it
19     params: Any = field(default_factory=dict)
20 
21     # cls is deprecated, use target, cls will be removed in Hydra 1.1
22     cls: str = MISSING
23 
24     # class is deprecated, use target, class will be removed in Hydra 1.1
25     # (class is Python keyword and is only supported through DictConfig)
26     # class: str = MISSING
27 
28 
29 class RunMode(Enum):
30     RUN = 1
31     MULTIRUN = 2
32
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/hydra/types.py b/hydra/types.py
--- a/hydra/types.py
+++ b/hydra/types.py
@@ -18,13 +18,6 @@
     # parameters to pass to cls when calling it
     params: Any = field(default_factory=dict)
 
-    # cls is deprecated, use target, cls will be removed in Hydra 1.1
-    cls: str = MISSING
-
-    # class is deprecated, use target, class will be removed in Hydra 1.1
-    # (class is Python keyword and is only supported through DictConfig)
-    # class: str = MISSING
-
 
 class RunMode(Enum):
     RUN = 1

{"golden_diff": "diff --git a/hydra/types.py b/hydra/types.py\n--- a/hydra/types.py\n+++ b/hydra/types.py\n@@ -18,13 +18,6 @@\n     # parameters to pass to cls when calling it\n     params: Any = field(default_factory=dict)\n \n-    # cls is deprecated, use target, cls will be removed in Hydra 1.1\n-    cls: str = MISSING\n-\n-    # class is deprecated, use target, class will be removed in Hydra 1.1\n-    # (class is Python keyword and is only supported through DictConfig)\n-    # class: str = MISSING\n-\n \n class RunMode(Enum):\n     RUN = 1\n", "issue": "[Bug] MISSING for Object Conf cls argument\n# \ud83d\udc1b Bug\r\n\r\nOmegaConf cls argument should not be a mandatory value if target is defined. Can we change this to be an optional value with None being the default?\r\n \r\n** Stack trace/error message **\r\n```\r\nomegaconf.errors.MissingMandatoryValue: Missing mandatory value: scheduler.cls\r\n        full_key: scheduler.cls\r\n        reference_type=ObjectConf\r\n        object_type=ObjectConf\r\n```\r\n\r\n\r\n## System information\r\n- **Hydra Version** :  1.0.0rc2\r\n- **Python version** : 3.7.7\r\n\n", "before_files": [{"content": "# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved\nfrom dataclasses import dataclass, field\nfrom enum import Enum\nfrom typing import Any, Callable, Dict\n\nfrom omegaconf import MISSING\n\nTaskFunction = Callable[[Any], Any]\n\n\n@dataclass\n# This extends Dict[str, Any] to allow for the deprecated \"class\" field.\n# Once support for class field removed this can stop extending Dict.\nclass ObjectConf(Dict[str, Any]):\n    # class, class method or function name\n    target: str = MISSING\n\n    # parameters to pass to cls when calling it\n    params: Any = field(default_factory=dict)\n\n    # cls is deprecated, use target, cls will be removed in Hydra 1.1\n    cls: str = MISSING\n\n    # class is deprecated, use target, class will be removed in Hydra 1.1\n    # (class is Python keyword and is only supported through DictConfig)\n    # class: str = MISSING\n\n\nclass RunMode(Enum):\n    RUN = 1\n    MULTIRUN = 2\n", "path": "hydra/types.py"}], "after_files": [{"content": "# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved\nfrom dataclasses import dataclass, field\nfrom enum import Enum\nfrom typing import Any, Callable, Dict\n\nfrom omegaconf import MISSING\n\nTaskFunction = Callable[[Any], Any]\n\n\n@dataclass\n# This extends Dict[str, Any] to allow for the deprecated \"class\" field.\n# Once support for class field removed this can stop extending Dict.\nclass ObjectConf(Dict[str, Any]):\n    # class, class method or function name\n    target: str = MISSING\n\n    # parameters to pass to cls when calling it\n    params: Any = field(default_factory=dict)\n\n\nclass RunMode(Enum):\n    RUN = 1\n    MULTIRUN = 2\n", "path": "hydra/types.py"}]}