Base class alternative to ExtensibleObject for objects customizable through the metadata system.
Similar to ExtensibleObject: the describe() method provides access to the related object-type metadata.
The getCustom() method is the central point to retrieve and store the objects attribute
values themselves.
Returns the meta data of this object. If no meta data is available the
method returns null. The returned ObjectTypeDefinition can be used to
retrieve the metadata for any of the custom attributes.
Returns:
the meta data of this object. If no meta data is available the
method returns null.