code: def prepare(base_path='data',
              serialize=json.dumps,
              deserialize=json.loads,
              file_ext='json'):
      
      global _basepath, _deserialize, _serialize, _ext
      _basepath = base_path
      assert callable(serialize)
      assert callable(deserialize)
      _serialize = serialize
      _deserialize = deserialize
      _ext = file_ext
      _logger.debug('preparing with base path %s and file ext %s',
          _basepath, _ext)
      assert len(_db)
      for collection in _db.keys():
          c_path = collection_path(collection)
          os.makedirs(c_path, exist_ok=True)
          _logger.info('collection "%s": %d objects',
              collection, object_count(collection))
docs: After you have added your collections, prepare the database
      for use.