We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Add type check to Identity Function
Related to #123


--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `chainer/functions/identity.py`
Content:
```
1 from chainer import function
2 
3 
4 class Identity(function.Function):
5 
6     """Identity function."""
7 
8     def forward(self, xs):
9         return xs
10 
11     def backward(self, xs, gys):
12         return gys
13 
14 
15 def identity(*inputs):
16     """Just returns input variables."""
17     return Identity()(*inputs)
18
```
--- 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/chainer/functions/identity.py b/chainer/functions/identity.py
--- a/chainer/functions/identity.py
+++ b/chainer/functions/identity.py
@@ -5,6 +5,9 @@
 
     """Identity function."""
 
+    def check_type_forward(self, in_types):
+        pass
+
     def forward(self, xs):
         return xs

{"golden_diff": "diff --git a/chainer/functions/identity.py b/chainer/functions/identity.py\n--- a/chainer/functions/identity.py\n+++ b/chainer/functions/identity.py\n@@ -5,6 +5,9 @@\n \n     \"\"\"Identity function.\"\"\"\n \n+    def check_type_forward(self, in_types):\n+        pass\n+\n     def forward(self, xs):\n         return xs\n", "issue": "Add type check to Identity Function\nRelated to #123\n\n", "before_files": [{"content": "from chainer import function\n\n\nclass Identity(function.Function):\n\n    \"\"\"Identity function.\"\"\"\n\n    def forward(self, xs):\n        return xs\n\n    def backward(self, xs, gys):\n        return gys\n\n\ndef identity(*inputs):\n    \"\"\"Just returns input variables.\"\"\"\n    return Identity()(*inputs)\n", "path": "chainer/functions/identity.py"}], "after_files": [{"content": "from chainer import function\n\n\nclass Identity(function.Function):\n\n    \"\"\"Identity function.\"\"\"\n\n    def check_type_forward(self, in_types):\n        pass\n\n    def forward(self, xs):\n        return xs\n\n    def backward(self, xs, gys):\n        return gys\n\n\ndef identity(*inputs):\n    \"\"\"Just returns input variables.\"\"\"\n    return Identity()(*inputs)\n", "path": "chainer/functions/identity.py"}]}