@staticmethod<EOL><INDENT>def timestamp_insert(sender, frames):<DEDENT>
for frame in frames:<EOL><INDENT>timestamp = datetime.now(timezone.utc)<EOL>frame.created = timestamp<EOL>frame.modified = timestamp<EOL><DEDENT>
Timestamp the created and modified fields for all documents. This method
should be bound to a frame class like so:

```
MyFrameClass.listen('insert', MyFrameClass.timestamp_insert)
```