API Docs: Add some more precisions about calling __init__ for Blender-derined classes.

Hopefully will avoid confusion like in #134600.

doc/python_api/rst/info_overview.rst

@@ -202,8 +202,14 @@ otherwise Blender's internal initialization won't happen properly:
    class AwesomeRaytracer(bpy.types.RenderEngine):
       def __init__(self, *args, **kwargs):
          super().__init__(*args, **kwargs)
+         self.my_var = 42
          ...
 
+.. warning::
+
+   The Blender-defined parent constructor must be called before any data access to the object, including
+   from other potential parent types ``__init__()`` functions.
+
 .. warning::
 
    Calling the parent's ``__init__()`` function is a hard requirement since Blender 4.4.
@@ -223,8 +229,9 @@ otherwise Blender's internal initialization won't happen properly:
 
 .. note::
 
-   In case you are using complex/multi-inheritance, ``super()`` may not work. It is best then to
-   explicitly invoke the Blender-defined parent class constructor. For example:
+   In case you are using complex/multi-inheritance, ``super()`` may not work (as the Blender-defined parent
+   may not be the first type in the MRO). It is best then to first explicitly invoke the Blender-defined
+   parent class constructor, before any other. For example:
 
    .. code-block:: python
 
@@ -232,6 +239,8 @@ otherwise Blender's internal initialization won't happen properly:
       class FancyRaytracer(AwesomeRaytracer, bpy.types.RenderEngine):
          def __init__(self, *args, **kwargs):
             bpy.types.RenderEngine.__init__(self, *args, **kwargs)
+            AwesomeRaytracer.__init__(self, *args, **kwargs)
+            self.my_var = 42
             ...
 
 .. note::