code: def getheader(self, which, use_hash=None, polish=True):
          
          header = getheader(
              which,
              use_hash=use_hash,
              target=self.target,
              no_tco=self.no_tco,
              strict=self.strict,
          )
          if polish:
              header = self.polish(header)
          return header
docs: Get a formatted header.