The subject of the email(s)

        :param value: The subject of the email(s)
        :type value: Subject, string

def subject(self, value):
        """The subject of the email(s)

        :param value: The subject of the email(s)
        :type value: Subject, string
        """
        if isinstance(value, Subject):
            if value.personalization is not None:
                try:
                    personalization = \
                        self._personalizations[value.personalization]
                    has_internal_personalization = True
                except IndexError:
                    personalization = Personalization()
                    has_internal_personalization = False
                personalization.subject = value.subject

                if not has_internal_personalization:
                    self.add_personalization(
                        personalization,
                        index=value.personalization)
            else:
                self._subject = value
        else:
            self._subject = Subject(value)