docs: def mixin(self):
          """
          Add the annotations to the ODM Element (if defined)
          :return: 
          """
          if self.milestones:
              from rwslib.builders.clinicaldata import Annotation, Flag, FlagValue
              annotation = Annotation()
              for codelist, milestones in self.milestones.items():
                  for milestone in milestones:
                      annotation << Flag() << FlagValue(milestone, codelist_oid=codelist)
              self.annotations.append(annotation)