'Virtual Field to allow Reporting by Age Group
@param row: a Row containing the person record
@ToDo: This formula might need to be different for different Orgs
or Usecases
@ToDo: If we need to be able to Filter based on these then we should
create a \'Named Range\' widget for an S3DateTimeFilter field'

@classmethod
def pr_person_age_group(cls, row):

    age = cls.pr_age(row)
    if ((age is None) or (age < 0)):
        return current.messages['NONE']
    else:
        return current.deployment_settings.get_pr_age_group(age)
