document calling operators with undo enabled.

doc/python_api/examples/bpy.ops.2.py

@@ -1,17 +1,22 @@
 """
-Overriding Context
-++++++++++++++++++
+Execution Context
+-----------------
 
-It is possible to override context members that the operator sees, so that they
-act on specified rather than the selected or active data, or to execute an
-operator in the different part of the user interface.
+When calling an operator you may want to pass the execution context.
 
-The context overrides are passed as a dictionary, with keys matching the context
-member names in bpy.context. For example to override bpy.context.active_object,
-you would pass {'active_object': object}.
+This determines the context thats given to the operator to run in, and weather
+invoke() is called or execute().
+
+'EXEC_DEFAULT' is used by default but you may want the operator to take user
+interaction with 'INVOKE_DEFAULT'.
+
+The execution context is as a non keyword, string argument in:
+('INVOKE_DEFAULT', 'INVOKE_REGION_WIN', 'INVOKE_REGION_CHANNELS',
+'INVOKE_REGION_PREVIEW', 'INVOKE_AREA', 'INVOKE_SCREEN', 'EXEC_DEFAULT',
+'EXEC_REGION_WIN', 'EXEC_REGION_CHANNELS', 'EXEC_REGION_PREVIEW', 'EXEC_AREA',
+'EXEC_SCREEN')
 """
 
-# remove all objects in scene rather than the selected ones
+# group add popup
 import bpy
-override = {'selected_bases': list(bpy.context.scene.object_bases)}
-bpy.ops.object.delete(override)
+bpy.ops.object.group_instance_add('INVOKE_DEFAULT')