code: def receivers(self):
          
          attrs = (
              ['Resent-To', 'Resent-Cc', 'Resent-Bcc'] if self.resent else
              ['To', 'Cc', 'Bcc']
          )
          addrs = (v for v in (self.get(k) for k in attrs) if v)
          return [addr for _, addr in getaddresses(addrs)]
docs: Returns a list of receivers, obtained from the
          To, Cc, and Bcc headers, respecting the Resent-*
          headers if the email was resent.