docs: def _make_digest(k, **kwargs):
      """
      Creates a digest suitable for use within an :class:`phyles.FSCache`
      object from the key object `k`.
  
      >>> adict = {'a' : {'b':1}, 'f': []}
      >>> make_digest(adict)
      'a2VKynHgDrUIm17r6BQ5QcA5XVmqpNBmiKbZ9kTu0A'
      """
      result = list()
      result_dict = _make_digest_dict(k, **kwargs)
      if result_dict is None:
          return 'default'
      else: 
          for (key, h) in sorted(result_dict.items()):
              result.append('{}_{}'.format(key, h))
          return '.'.join(result)