We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Remove trigger option of snapshot and snapshot_object
They have the same functionality as the trigger argument of Trainer.extend and are redundant. I think they confuse users and they might misunderstand the trigger feature, and so they should be removed in the next major update.

--- 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/training/extensions/_snapshot.py`
Content:
```
1 import os
2 import shutil
3 import tempfile
4 
5 from chainer.serializers import npz
6 from chainer.training import extension
7 
8 
9 def snapshot_object(target, filename, savefun=npz.save_npz,
10                     trigger=(1, 'epoch')):
11     """Returns a trainer extension to take snapshots of a given object.
12 
13     This extension serializes the given object and saves it to the output
14     directory.
15 
16     This extension is called once for each epoch by default. The default
17     priority is -100, which is lower than that of most built-in extensions.
18 
19     Args:
20         target: Object to serialize.
21         filename (str): Name of the file into which the object is serialized.
22             It can be a format string, where the trainer object is passed to
23             the :meth:`str.format` method. For example,
24             ``'snapshot_{.updater.iteration}'`` is converted to
25             ``'snapshot_10000'`` at the 10,000th iteration.
26         savefun: Function to save the object. It takes two arguments: the
27             output file path and the object to serialize.
28         trigger: Trigger that decides when to take snapshot. It can be either
29             an already built trigger object (i.e., a callable object that
30             accepts a trainer object and returns a bool value), or a tuple in
31             the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter
32             case, the tuple is passed to IntervalTrigger.
33 
34     Returns:
35         An extension function.
36 
37     """
38     @extension.make_extension(trigger=trigger, priority=-100)
39     def snapshot_object(trainer):
40         _snapshot_object(trainer, target, filename.format(trainer), savefun)
41 
42     return snapshot_object
43 
44 
45 def snapshot(savefun=npz.save_npz,
46              filename='snapshot_iter_{.updater.iteration}',
47              trigger=(1, 'epoch')):
48     """Returns a trainer extension to take snapshots of the trainer.
49 
50     This extension serializes the trainer object and saves it to the output
51     directory. It is used to support resuming the training loop from the saved
52     state.
53 
54     This extension is called once for each epoch by default. The default
55     priority is -100, which is lower than that of most built-in extensions.
56 
57     .. note::
58        This extension first writes the serialized object to a temporary file
59        and then rename it to the target file name. Thus, if the program stops
60        right before the renaming, the temporary file might be left in the
61        output directory.
62 
63     Args:
64         savefun: Function to save the trainer. It takes two arguments: the
65             output file path and the trainer object.
66         filename (str): Name of the file into which the trainer is serialized.
67             It can be a format string, where the trainer object is passed to
68             the :meth:`str.format` method.
69         trigger: Trigger that decides when to take snapshot. It can be either
70             an already built trigger object (i.e., a callable object that
71             accepts a trainer object and returns a bool value), or a tuple in
72             the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter
73             case, the tuple is passed to IntervalTrigger.
74 
75     """
76     @extension.make_extension(trigger=trigger, priority=-100)
77     def snapshot(trainer):
78         _snapshot_object(trainer, trainer, filename.format(trainer), savefun)
79 
80     return snapshot
81 
82 
83 def _snapshot_object(trainer, target, filename, savefun):
84     fn = filename.format(trainer)
85     prefix = 'tmp' + fn
86     fd, tmppath = tempfile.mkstemp(prefix=prefix, dir=trainer.out)
87     try:
88         savefun(tmppath, target)
89     except Exception:
90         os.close(fd)
91         os.remove(tmppath)
92         raise
93     os.close(fd)
94     shutil.move(tmppath, os.path.join(trainer.out, fn))
95
```
--- 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/training/extensions/_snapshot.py b/chainer/training/extensions/_snapshot.py
--- a/chainer/training/extensions/_snapshot.py
+++ b/chainer/training/extensions/_snapshot.py
@@ -6,15 +6,19 @@
 from chainer.training import extension
 
 
-def snapshot_object(target, filename, savefun=npz.save_npz,
-                    trigger=(1, 'epoch')):
+def snapshot_object(target, filename, savefun=npz.save_npz):
     """Returns a trainer extension to take snapshots of a given object.
 
     This extension serializes the given object and saves it to the output
     directory.
 
-    This extension is called once for each epoch by default. The default
-    priority is -100, which is lower than that of most built-in extensions.
+    This extension is called once per epoch by default. To take a
+    snapshot at a different interval, a trigger object specifying the
+    required interval can be passed along with this extension
+    to the `extend()` method of the trainer.
+
+    The default priority is -100, which is lower than that of most
+    built-in extensions.
 
     Args:
         target: Object to serialize.
@@ -25,17 +29,12 @@
             ``'snapshot_10000'`` at the 10,000th iteration.
         savefun: Function to save the object. It takes two arguments: the
             output file path and the object to serialize.
-        trigger: Trigger that decides when to take snapshot. It can be either
-            an already built trigger object (i.e., a callable object that
-            accepts a trainer object and returns a bool value), or a tuple in
-            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter
-            case, the tuple is passed to IntervalTrigger.
 
     Returns:
         An extension function.
 
     """
-    @extension.make_extension(trigger=trigger, priority=-100)
+    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)
     def snapshot_object(trainer):
         _snapshot_object(trainer, target, filename.format(trainer), savefun)
 
@@ -43,16 +42,20 @@
 
 
 def snapshot(savefun=npz.save_npz,
-             filename='snapshot_iter_{.updater.iteration}',
-             trigger=(1, 'epoch')):
+             filename='snapshot_iter_{.updater.iteration}'):
     """Returns a trainer extension to take snapshots of the trainer.
 
     This extension serializes the trainer object and saves it to the output
     directory. It is used to support resuming the training loop from the saved
     state.
 
-    This extension is called once for each epoch by default. The default
-    priority is -100, which is lower than that of most built-in extensions.
+    This extension is called once per epoch by default. To take a
+    snapshot at a different interval, a trigger object specifying the
+    required interval can be passed along with this extension
+    to the `extend()` method of the trainer.
+
+    The default priority is -100, which is lower than that of most
+    built-in extensions.
 
     .. note::
        This extension first writes the serialized object to a temporary file
@@ -66,14 +69,9 @@
         filename (str): Name of the file into which the trainer is serialized.
             It can be a format string, where the trainer object is passed to
             the :meth:`str.format` method.
-        trigger: Trigger that decides when to take snapshot. It can be either
-            an already built trigger object (i.e., a callable object that
-            accepts a trainer object and returns a bool value), or a tuple in
-            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter
-            case, the tuple is passed to IntervalTrigger.
 
     """
-    @extension.make_extension(trigger=trigger, priority=-100)
+    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)
     def snapshot(trainer):
         _snapshot_object(trainer, trainer, filename.format(trainer), savefun)

{"golden_diff": "diff --git a/chainer/training/extensions/_snapshot.py b/chainer/training/extensions/_snapshot.py\n--- a/chainer/training/extensions/_snapshot.py\n+++ b/chainer/training/extensions/_snapshot.py\n@@ -6,15 +6,19 @@\n from chainer.training import extension\n \n \n-def snapshot_object(target, filename, savefun=npz.save_npz,\n-                    trigger=(1, 'epoch')):\n+def snapshot_object(target, filename, savefun=npz.save_npz):\n     \"\"\"Returns a trainer extension to take snapshots of a given object.\n \n     This extension serializes the given object and saves it to the output\n     directory.\n \n-    This extension is called once for each epoch by default. The default\n-    priority is -100, which is lower than that of most built-in extensions.\n+    This extension is called once per epoch by default. To take a\n+    snapshot at a different interval, a trigger object specifying the\n+    required interval can be passed along with this extension\n+    to the `extend()` method of the trainer.\n+\n+    The default priority is -100, which is lower than that of most\n+    built-in extensions.\n \n     Args:\n         target: Object to serialize.\n@@ -25,17 +29,12 @@\n             ``'snapshot_10000'`` at the 10,000th iteration.\n         savefun: Function to save the object. It takes two arguments: the\n             output file path and the object to serialize.\n-        trigger: Trigger that decides when to take snapshot. It can be either\n-            an already built trigger object (i.e., a callable object that\n-            accepts a trainer object and returns a bool value), or a tuple in\n-            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter\n-            case, the tuple is passed to IntervalTrigger.\n \n     Returns:\n         An extension function.\n \n     \"\"\"\n-    @extension.make_extension(trigger=trigger, priority=-100)\n+    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)\n     def snapshot_object(trainer):\n         _snapshot_object(trainer, target, filename.format(trainer), savefun)\n \n@@ -43,16 +42,20 @@\n \n \n def snapshot(savefun=npz.save_npz,\n-             filename='snapshot_iter_{.updater.iteration}',\n-             trigger=(1, 'epoch')):\n+             filename='snapshot_iter_{.updater.iteration}'):\n     \"\"\"Returns a trainer extension to take snapshots of the trainer.\n \n     This extension serializes the trainer object and saves it to the output\n     directory. It is used to support resuming the training loop from the saved\n     state.\n \n-    This extension is called once for each epoch by default. The default\n-    priority is -100, which is lower than that of most built-in extensions.\n+    This extension is called once per epoch by default. To take a\n+    snapshot at a different interval, a trigger object specifying the\n+    required interval can be passed along with this extension\n+    to the `extend()` method of the trainer.\n+\n+    The default priority is -100, which is lower than that of most\n+    built-in extensions.\n \n     .. note::\n        This extension first writes the serialized object to a temporary file\n@@ -66,14 +69,9 @@\n         filename (str): Name of the file into which the trainer is serialized.\n             It can be a format string, where the trainer object is passed to\n             the :meth:`str.format` method.\n-        trigger: Trigger that decides when to take snapshot. It can be either\n-            an already built trigger object (i.e., a callable object that\n-            accepts a trainer object and returns a bool value), or a tuple in\n-            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter\n-            case, the tuple is passed to IntervalTrigger.\n \n     \"\"\"\n-    @extension.make_extension(trigger=trigger, priority=-100)\n+    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)\n     def snapshot(trainer):\n         _snapshot_object(trainer, trainer, filename.format(trainer), savefun)\n", "issue": "Remove trigger option of snapshot and snapshot_object\nThey have the same functionality as the trigger argument of Trainer.extend and are redundant. I think they confuse users and they might misunderstand the trigger feature, and so they should be removed in the next major update.\n", "before_files": [{"content": "import os\nimport shutil\nimport tempfile\n\nfrom chainer.serializers import npz\nfrom chainer.training import extension\n\n\ndef snapshot_object(target, filename, savefun=npz.save_npz,\n                    trigger=(1, 'epoch')):\n    \"\"\"Returns a trainer extension to take snapshots of a given object.\n\n    This extension serializes the given object and saves it to the output\n    directory.\n\n    This extension is called once for each epoch by default. The default\n    priority is -100, which is lower than that of most built-in extensions.\n\n    Args:\n        target: Object to serialize.\n        filename (str): Name of the file into which the object is serialized.\n            It can be a format string, where the trainer object is passed to\n            the :meth:`str.format` method. For example,\n            ``'snapshot_{.updater.iteration}'`` is converted to\n            ``'snapshot_10000'`` at the 10,000th iteration.\n        savefun: Function to save the object. It takes two arguments: the\n            output file path and the object to serialize.\n        trigger: Trigger that decides when to take snapshot. It can be either\n            an already built trigger object (i.e., a callable object that\n            accepts a trainer object and returns a bool value), or a tuple in\n            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter\n            case, the tuple is passed to IntervalTrigger.\n\n    Returns:\n        An extension function.\n\n    \"\"\"\n    @extension.make_extension(trigger=trigger, priority=-100)\n    def snapshot_object(trainer):\n        _snapshot_object(trainer, target, filename.format(trainer), savefun)\n\n    return snapshot_object\n\n\ndef snapshot(savefun=npz.save_npz,\n             filename='snapshot_iter_{.updater.iteration}',\n             trigger=(1, 'epoch')):\n    \"\"\"Returns a trainer extension to take snapshots of the trainer.\n\n    This extension serializes the trainer object and saves it to the output\n    directory. It is used to support resuming the training loop from the saved\n    state.\n\n    This extension is called once for each epoch by default. The default\n    priority is -100, which is lower than that of most built-in extensions.\n\n    .. note::\n       This extension first writes the serialized object to a temporary file\n       and then rename it to the target file name. Thus, if the program stops\n       right before the renaming, the temporary file might be left in the\n       output directory.\n\n    Args:\n        savefun: Function to save the trainer. It takes two arguments: the\n            output file path and the trainer object.\n        filename (str): Name of the file into which the trainer is serialized.\n            It can be a format string, where the trainer object is passed to\n            the :meth:`str.format` method.\n        trigger: Trigger that decides when to take snapshot. It can be either\n            an already built trigger object (i.e., a callable object that\n            accepts a trainer object and returns a bool value), or a tuple in\n            the form ``<int>, 'epoch'`` or ``<int>, 'iteration'``. In latter\n            case, the tuple is passed to IntervalTrigger.\n\n    \"\"\"\n    @extension.make_extension(trigger=trigger, priority=-100)\n    def snapshot(trainer):\n        _snapshot_object(trainer, trainer, filename.format(trainer), savefun)\n\n    return snapshot\n\n\ndef _snapshot_object(trainer, target, filename, savefun):\n    fn = filename.format(trainer)\n    prefix = 'tmp' + fn\n    fd, tmppath = tempfile.mkstemp(prefix=prefix, dir=trainer.out)\n    try:\n        savefun(tmppath, target)\n    except Exception:\n        os.close(fd)\n        os.remove(tmppath)\n        raise\n    os.close(fd)\n    shutil.move(tmppath, os.path.join(trainer.out, fn))\n", "path": "chainer/training/extensions/_snapshot.py"}], "after_files": [{"content": "import os\nimport shutil\nimport tempfile\n\nfrom chainer.serializers import npz\nfrom chainer.training import extension\n\n\ndef snapshot_object(target, filename, savefun=npz.save_npz):\n    \"\"\"Returns a trainer extension to take snapshots of a given object.\n\n    This extension serializes the given object and saves it to the output\n    directory.\n\n    This extension is called once per epoch by default. To take a\n    snapshot at a different interval, a trigger object specifying the\n    required interval can be passed along with this extension\n    to the `extend()` method of the trainer.\n\n    The default priority is -100, which is lower than that of most\n    built-in extensions.\n\n    Args:\n        target: Object to serialize.\n        filename (str): Name of the file into which the object is serialized.\n            It can be a format string, where the trainer object is passed to\n            the :meth:`str.format` method. For example,\n            ``'snapshot_{.updater.iteration}'`` is converted to\n            ``'snapshot_10000'`` at the 10,000th iteration.\n        savefun: Function to save the object. It takes two arguments: the\n            output file path and the object to serialize.\n\n    Returns:\n        An extension function.\n\n    \"\"\"\n    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)\n    def snapshot_object(trainer):\n        _snapshot_object(trainer, target, filename.format(trainer), savefun)\n\n    return snapshot_object\n\n\ndef snapshot(savefun=npz.save_npz,\n             filename='snapshot_iter_{.updater.iteration}'):\n    \"\"\"Returns a trainer extension to take snapshots of the trainer.\n\n    This extension serializes the trainer object and saves it to the output\n    directory. It is used to support resuming the training loop from the saved\n    state.\n\n    This extension is called once per epoch by default. To take a\n    snapshot at a different interval, a trigger object specifying the\n    required interval can be passed along with this extension\n    to the `extend()` method of the trainer.\n\n    The default priority is -100, which is lower than that of most\n    built-in extensions.\n\n    .. note::\n       This extension first writes the serialized object to a temporary file\n       and then rename it to the target file name. Thus, if the program stops\n       right before the renaming, the temporary file might be left in the\n       output directory.\n\n    Args:\n        savefun: Function to save the trainer. It takes two arguments: the\n            output file path and the trainer object.\n        filename (str): Name of the file into which the trainer is serialized.\n            It can be a format string, where the trainer object is passed to\n            the :meth:`str.format` method.\n\n    \"\"\"\n    @extension.make_extension(trigger=(1, 'epoch'), priority=-100)\n    def snapshot(trainer):\n        _snapshot_object(trainer, trainer, filename.format(trainer), savefun)\n\n    return snapshot\n\n\ndef _snapshot_object(trainer, target, filename, savefun):\n    fn = filename.format(trainer)\n    prefix = 'tmp' + fn\n    fd, tmppath = tempfile.mkstemp(prefix=prefix, dir=trainer.out)\n    try:\n        savefun(tmppath, target)\n    except Exception:\n        os.close(fd)\n        os.remove(tmppath)\n        raise\n    os.close(fd)\n    shutil.move(tmppath, os.path.join(trainer.out, fn))\n", "path": "chainer/training/extensions/_snapshot.py"}]}