code: def parse_trailer(header):
      
      pos = 0
      names = []
      while pos < len(header):
          name, pos = expect_re(re_token, header, pos)
          if name:
              names.append(name)
          _, pos = accept_ws(header, pos)
          _, pos = expect_lit(',', header, pos)
          _, pos = accept_ws(header, pos)
      return names
docs: Parse the "Trailer" header.