Indicates if this object is still valid, i.e. hasn't been deleted or some other action done to invalidate the reference.
"constructionPlaneThreePointsDefinition_var" is a variable referencing a ConstructionPlaneThreePointsDefinition object. | 
        
"constructionPlaneThreePointsDefinition_var" is a variable referencing a ConstructionPlaneThreePointsDefinition object. |