Added docs for subclassing and lifecycle hooks

docs/source/extensions/example_extension/01b_basic_structure_subclass.py

@@ -0,0 +1,41 @@
+from labthings.server.extensions import BaseExtension
+from labthings.server.find import find_component
+
+
+# Create the extension class
+class MyExtension(BaseExtension):
+    def __init__(self):
+
+        # Create some instance variable
+        self.state_variable = "An example of a persistant instance variable"
+
+        # Superclass init function
+        super().__init__("com.myname.myextension", version="0.0.0")
+
+    def identify(self):
+        """
+        Demonstrate access to Microscope.camera, and Microscope.stage
+        """
+        microscope = find_component("org.openflexure.microscope")
+
+        response = (
+            f"My name is {microscope.name}. "
+            f"My parent camera is {microscope.camera}, "
+            f"and my parent stage is {microscope.stage}."
+        )
+
+        return response
+
+    def rename(self, new_name):
+        """
+        Rename the microscope
+        """
+
+        microscope = find_component("org.openflexure.microscope")
+
+        microscope.name = new_name
+        microscope.save_settings()
+
+
+# Create your extension object
+my_extension = MyExtension()