docs: def get_primary_contributors(self):
          """
          Returns a list of primary contributors, with primary being defined
          as those contributors that have the highest role assigned (in terms
          of priority). Only permitted contributors are returned.
          """
          primary_credits = []
          credits = self.credits.exclude(credit_option=None).order_by(
              'credit_option__role_priority'
          )
          if credits:
              primary_role_priority = credits[0].credit_option.role_priority
              for credit in credits:
                  if credit.credit_option.role_priority == primary_role_priority:
                      primary_credits.append(credit)
  
          contributors = []
          for credit in primary_credits:
              contributor = credit.contributor
              if contributor.is_permitted:
                  contributors.append(contributor)
  
          return contributors