prompt: 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()
  
  ```
  
golden_diff: 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
  
verification_info: {"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"}]}