docs: def set_mimetext_headers(self, message, subject, from_addr, to_addrs, cc_addrs, priority):
          """Sets headers on Mimetext message"""
  
          message['Subject'] = subject
          message['From'] = from_addr
          message['To'] = ', '.join(to_addrs)
          if cc_addrs:
              message['Cc'] = ', '.join(cc_addrs)
  
          if priority and self.priority_header_is_valid(priority):
              priority = PRIORITIES[str(priority)].copy()
              for key in priority:
                  message[key] = priority[key]
  
          return message