code: def get_random_filename(content_type=None):
      
      extension = mimetypes.guess_extension(content_type or '') or ''
      characters = string.ascii_letters + '0123456789'
      letters = ''.join(random.sample(characters, 8))
      name = 'planet-{}{}'.format(letters, extension)
      return name
docs: Get a pseudo-random, Planet-looking filename.
  
      >>> from planet.api import utils
      >>> print(utils.get_random_filename()) #doctest:+SKIP
      planet-61FPnh7K
      >>> print(utils.get_random_filename('image/tiff')) #doctest:+SKIP
      planet-V8ELYxy5.tif
      >>>
  
      :returns: a filename (i.e. ``basename``)
      :rtype: str