docs: def content_id(self, value):
          """The content id for the attachment.
  
          This is used when the disposition is set to "inline" and the attachment
          is an image, allowing the file to be displayed within the email body.
  
          :param content_id: The content id for the attachment.
                             This is used when the Disposition is set to "inline"
                             and the attachment is an image, allowing the file to
                             be displayed within the email body.
          :type content_id: ContentId, string, optional
          """
          if isinstance(value, ContentId):
              self._content_id = value
          else:
              self._content_id = ContentId(value)