Created Writing your own backends (markdown)

Writing-your-own-backends.md

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+You can also write your own backends, where a backend is nothing but a thread that listens for messages on a certain channel and pokes the main app whenever it receives one.
+
+1. Create your backend directory under `platypush/backend` (e.g. `voicemail`)
+
+2. In the case above, `platypush.backend.voicemail` will be your package name.
+
+3. Create an `__init__.py` under `platypush/backend/voicemail`.
+
+4. If your module is `voicemail`, then its main class should be named `VoicemailBackend`.
+
+5. The configuration for your module will be read from a section named `backend.voicemail` from your `config.yaml`. Its values will be passed over the backend constructor arguments.
+
+6. Implement the `run` method. Since a backend is a thread that polls for new messages on a channel, this will be the thread main method. `send_message` should call `self.on_message` at the end to post a new message to the application.
+
+7. Implement the `send_message` method. This method will be called whenever the application needs to send a new message through `send_request` and `send_response`. You should never call `send_message` directly.
+
+The `__init__.py` will look like this:
+
+```python
+from .. import Backend
+
+class VoicemailBackend(Backend)
+    def __init__(self, phone)
+        super().__init__()
+        self.phone = phone
+        self.voicemail = Voicemail(...)
+
+    def send_message(self, msg):
+        self.voicemail.save_msg(msg)
+
+    def run(self):
+        while True:
+            msg = self.voicemail.poll()
+            self.on_message(msg)
+```