doc update (add example)
diff --git a/documentation/pyserial_api.rst b/documentation/pyserial_api.rst
index 411a832..c23d837 100644
--- a/documentation/pyserial_api.rst
+++ b/documentation/pyserial_api.rst
@@ -1104,6 +1104,27 @@
 
         Closes serial port.
 
+Example::
+
+    class PrintLines(LineReader):
+        def connection_made(self, transport):
+            super(PrintLines, self).connection_made(transport)
+            sys.stdout.write('port opened\n')
+            self.write_line('hello world')
+
+        def handle_line(self, data):
+            sys.stdout.write('line received: {}\n'.format(repr(data)))
+
+        def connection_lost(self, exc):
+            if exc:
+                traceback.print_exc(exc)
+            sys.stdout.write('port closed\n')
+
+    ser = serial.serial_for_url('loop://', baudrate=115200, timeout=1)
+    with SerialPortWorker(ser, PrintLines) as protocol:
+        protocol.write_line('hello')
+        time.sleep(2)
+
 
 asyncio
 =======