Update network backend examples to use httpcore.MackBackend

Author: Patrick J. McNerthney

docs/advanced/transports.md

@@ -38,13 +38,14 @@ connecting via a Unix Domain Socket that is only available via this low-level AP
 Another advanced configuration is supplying a custom httpcore [Network Backend](https://www.encode.io/httpcore/network-backends/).
 
 ```pycon
+>>> import httpcore
 >>> import httpx
->>> import myk8s
->>> # This custom network backend enables remote access to ports inside a Kubernetes Cluster using pod port forwarding.
->>> backend = myk8s.NetworkBackend('cluster.local')
+>>> backend = httpcore.MockBackend([b"HTTP/1.1 200 OK\r\n\r\nHello, World!"])
 >>> transport = httpx.HTTPTransport(network_backend=backend)
 >>> client = httpx.Client(transport=transport)
->>> response = client.get("http://argocd-server.argocd.svc.cluster.local")
+>>> response = client.get("http://network-backend")
+>>> reposne.text
+'Hello, World!'
 ```
 
 ## WSGI Transport

httpx/_transports/default.py

@@ -25,11 +25,12 @@
 client = httpx.Client(transport=transport)
 
 # Using advanced httpcore configuration, with custom network backend.
-import myk8s
-backend = myk8s.NetworkBackend('cluster.local')
+import httpcore
+backend = backend = httpcore.MockBackend([b"HTTP/1.1 200 OK\r\n\r\nHello, World!"])
 transport = httpx.HTTPTransport(network_backend=backend)
 client = httpx.Client(transport=transport)
-response = client.get("http://argocd-server.argocd.svc.cluster.local")
+response = client.get("http://network-backend")
+content = response.text
 """
 
 from __future__ import annotations