code: def is_vimball(fd):
      
      fd.seek(0)
      try:
          header = fd.readline()
      except UnicodeDecodeError:
          # binary files will raise exceptions when trying to decode raw bytes to
          # str objects in our readline() wrapper
          return False
      if re.match('^" Vimball Archiver', header) is not None:
          return True
      return False
docs: Test for vimball archive format compliance.
  
      Simple check to see if the first line of the file starts with standard
      vimball archive header.