We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
`Function` which get no input cannot select `volatile`
In `Function.__call__`, it checks `volatile` of all input variables, and the same value is used. But, `Function` which get not argument such as `Parameter`, always selects `volatile=False`. it may causes conflict of volatility.

https://github.com/pfnet/chainer/blob/master/chainer/function.py#L132
`Parameter` always returns `False` here.


--- 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/parameter.py`
Content:
```
1 import numpy
2 
3 from chainer import function
4 from chainer.utils import type_check
5 
6 
7 class Parameter(function.Function):
8 
9     """Function that outputs its weight array.
10 
11     This is a parameterized function that takes no input and returns a variable
12     holding a shallow copy of the parameter array.
13 
14     Args:
15         array: Initial parameter array.
16 
17     """
18     parameter_names = 'W',
19     gradient_names = 'gW',
20 
21     def __init__(self, array):
22         self.W = array
23         self.gW = numpy.empty_like(array)
24 
25     def check_type_forward(self, in_types):
26         type_check.expect(in_types.size() == 0)
27 
28     def forward(self, x):
29         return self.W,
30 
31     def backward(self, x, gy):
32         self.gW += gy[0]
33         return ()
34
```
--- 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/parameter.py b/chainer/functions/parameter.py
--- a/chainer/functions/parameter.py
+++ b/chainer/functions/parameter.py
@@ -22,6 +22,13 @@
         self.W = array
         self.gW = numpy.empty_like(array)
 
+    def __call__(self, volatile=False):
+        ret = super(Parameter, self).__call__()
+        if volatile:
+            ret.unchain_backward()
+        ret.volatile = volatile
+        return ret
+
     def check_type_forward(self, in_types):
         type_check.expect(in_types.size() == 0)

{"golden_diff": "diff --git a/chainer/functions/parameter.py b/chainer/functions/parameter.py\n--- a/chainer/functions/parameter.py\n+++ b/chainer/functions/parameter.py\n@@ -22,6 +22,13 @@\n         self.W = array\n         self.gW = numpy.empty_like(array)\n \n+    def __call__(self, volatile=False):\n+        ret = super(Parameter, self).__call__()\n+        if volatile:\n+            ret.unchain_backward()\n+        ret.volatile = volatile\n+        return ret\n+\n     def check_type_forward(self, in_types):\n         type_check.expect(in_types.size() == 0)\n", "issue": "`Function` which get no input cannot select `volatile`\nIn `Function.__call__`, it checks `volatile` of all input variables, and the same value is used. But, `Function` which get not argument such as `Parameter`, always selects `volatile=False`. it may causes conflict of volatility.\n\nhttps://github.com/pfnet/chainer/blob/master/chainer/function.py#L132\n`Parameter` always returns `False` here.\n\n", "before_files": [{"content": "import numpy\n\nfrom chainer import function\nfrom chainer.utils import type_check\n\n\nclass Parameter(function.Function):\n\n    \"\"\"Function that outputs its weight array.\n\n    This is a parameterized function that takes no input and returns a variable\n    holding a shallow copy of the parameter array.\n\n    Args:\n        array: Initial parameter array.\n\n    \"\"\"\n    parameter_names = 'W',\n    gradient_names = 'gW',\n\n    def __init__(self, array):\n        self.W = array\n        self.gW = numpy.empty_like(array)\n\n    def check_type_forward(self, in_types):\n        type_check.expect(in_types.size() == 0)\n\n    def forward(self, x):\n        return self.W,\n\n    def backward(self, x, gy):\n        self.gW += gy[0]\n        return ()\n", "path": "chainer/functions/parameter.py"}], "after_files": [{"content": "import numpy\n\nfrom chainer import function\nfrom chainer.utils import type_check\n\n\nclass Parameter(function.Function):\n\n    \"\"\"Function that outputs its weight array.\n\n    This is a parameterized function that takes no input and returns a variable\n    holding a shallow copy of the parameter array.\n\n    Args:\n        array: Initial parameter array.\n\n    \"\"\"\n    parameter_names = 'W',\n    gradient_names = 'gW',\n\n    def __init__(self, array):\n        self.W = array\n        self.gW = numpy.empty_like(array)\n\n    def __call__(self, volatile=False):\n        ret = super(Parameter, self).__call__()\n        if volatile:\n            ret.unchain_backward()\n        ret.volatile = volatile\n        return ret\n\n    def check_type_forward(self, in_types):\n        type_check.expect(in_types.size() == 0)\n\n    def forward(self, x):\n        return self.W,\n\n    def backward(self, x, gy):\n        self.gW += gy[0]\n        return ()\n", "path": "chainer/functions/parameter.py"}]}