Document dbus-python heritage and static method implementation

Point out that DBusMock objects are built on top of standard dbus-python
service objects, and thus can use all of its API.

Explain that AddMethod() is just a "remote control" API for dynamically
adding methods. Templates can also implement them in the usual static
way.

Author: martinpitt

README.md

@@ -220,6 +220,11 @@ with the template's convenience methods like
 or calling `AddObject()` yourself with the desired properties, of
 course.
 
+Templates commonly implement some non-trivial functionality with actual Python
+methods and the standard [dbus-python](https://dbus.freedesktop.org/doc/dbus-python/)
+[`@dbus.service.method`](https://dbus.freedesktop.org/doc/dbus-python/dbus.service.html#dbus.service.method)
+decorator.
+
 If you want to contribute a template, look at
 dbusmock/templates/upower.py for a real-life implementation. You can
 copy dbusmock/templates/SKELETON to your new template file name and

dbusmock/mockobject.py

@@ -126,6 +126,9 @@ class DBusMockObject(dbus.service.Object):  # pylint: disable=too-many-instance-
     This can be configured to have arbitrary methods (including code execution)
     and properties via methods on the org.freedesktop.DBus.Mock interface, so
     that you can control the mock from any programming language.
+
+    Beyond that "remote control" API, this is a standard dbus-python service object, see
+    <https://dbus.freedesktop.org/doc/dbus-python/tutorial.html#exporting-objects>.
     '''
 
     def __init__(self, bus_name: str, path: str, interface: str, props: PropsType,
@@ -262,7 +265,7 @@ def Set(self, interface_name: str, property_name: str, value: Any, *_, **__) ->
                          in_signature='ssa{sv}a(ssss)',
                          out_signature='')
     def AddObject(self, path: str, interface: str, properties: PropsType, methods: List[MethodType]) -> None:
-        '''Add a new D-Bus object to the mock
+        '''Dynamically add a new D-Bus object to the mock
 
         path: D-Bus object path
         interface: Primary D-Bus interface name of this object (where
@@ -359,7 +362,7 @@ def Reset(self) -> None:
                          in_signature='sssss',
                          out_signature='')
     def AddMethod(self, interface, name: str, in_sig: str, out_sig: str, code: str) -> None:
-        '''Add a method to this object
+        '''Dynamically add a method to this object
 
         interface: D-Bus interface to add this to. For convenience you can
                    specify '' here to add the method to the object's main
@@ -385,6 +388,14 @@ def AddMethod(self, interface, name: str, in_sig: str, out_sig: str, code: str)
 
               When specifying '', the method will not do anything (except
               logging) and return None.
+
+
+        This is meant for adding a method to a mock at runtime, from any programming language.
+        You can also use it in templates in the load() function.
+
+        For implementing non-trivial and static methods in templates, it is recommended to
+        implement them in the normal dbus-python way with using the @dbus.service.method
+        decorator instead.
         '''
         # pylint: disable=protected-access