Returns the Source (or ActionSource) object which is instantiated
by this clip. For example, if the clip is an instance of an action
source (ie., an animation or shape animation source item), then the
ActionSource object is returned. If
the clip is an instance of an audio or image source, the Source object is returned.
Note: The source returned here stores animation, audio, or image
data. This is not the same as the animation data that is driving
the parameter, such as an FCurve or a
ShapeKey. To access those DataSource elements, use the MappedItem.Source2 property on the
Clip.MappedItems collection
items.