Rewrite, edit and organize examples/websocket demos.

examples/websocket/public/derivatives_status.py

@@ -0,0 +1,23 @@
+# python -c "import examples.websocket.public.derivatives_status"
+
+from bfxapi import Client, PUB_WSS_HOST
+from bfxapi.websocket.enums import Error, Channel
+from bfxapi.websocket.types import DerivativesStatus
+
+from bfxapi.websocket import subscriptions
+
+bfx = Client(WSS_HOST=PUB_WSS_HOST)
+
+@bfx.wss.on("derivatives_status_update")
+def on_derivatives_status_update(subscription: subscriptions.Status, data: DerivativesStatus):
+  print(f"{subscription}:", data)
+
+@bfx.wss.on("wss-error")
+def on_wss_error(code: Error, msg: str):
+    print(code, msg)
+
+@bfx.wss.once("open")
+async def open():
+    await bfx.wss.subscribe(Channel.STATUS, key="deriv:tBTCF0:USTF0")
+
+bfx.wss.run()