code: def extract(self):
          
          if self.flags & v4c.FLAG_AT_EMBEDDED:
              if self.flags & v4c.FLAG_AT_COMPRESSED_EMBEDDED:
                  data = decompress(self.embedded_data)
              else:
                  data = self.embedded_data
              if self.flags & v4c.FLAG_AT_MD5_VALID:
                  md5_worker = md5()
                  md5_worker.update(data)
                  md5_sum = md5_worker.digest()
                  if self.md5_sum == md5_sum:
                      return data
                  else:
                      message = f"ATBLOCK md5sum={self.md5_sum} and embedded data md5sum={md5_sum}"
                      logger.warning(message)
              else:
                  return data
          else:
              logger.warning("external attachments not supported")
docs: extract attachment data
  
          Returns
          -------
          data : bytes