Derive Macro PlanningEntityImpl 

#[derive(PlanningEntityImpl)]
{
    // Attributes available to this derive:
    #[planning_id]
    #[planning_variable]
    #[planning_list_variable]
    #[planning_pin]
    #[inverse_relation_shadow_variable]
    #[previous_element_shadow_variable]
    #[next_element_shadow_variable]
    #[cascading_update_shadow_variable]
}