the `rfile` and `wfile` members are already implemented by
StreamRequestHandler. In addition to them several (undocumented)
class and instance variables exist according to
<https://github.com/python/cpython/blob/master/Lib/socketserver.py#L742>:
- `rbufsize`
- `wbufsize`
- `timeout`
- `disable_nagle_algorithm`
- `packet` and `socket` for datagrams
The already exist with Python 2.7
<https://github.com/python/cpython/blob/2.7/Lib/SocketServer.py#L677>
```mermaid
classDiagram
BaseRequestHandler <|-- DatagramRequestHandler
BaseRequestHandler <|-- StreamRequestHandler
StreamRequestHandler <|-- BaseHTTPRequestHandler
```
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