def load_cache(filename=None):
try:<EOL><INDENT>return AppEngineMemcache()<EOL><DEDENT>except ImportError:<EOL><INDENT>return PickleCache(filename)<EOL><DEDENT>
Loads cache system.

    If Google App Engine Standard Environment's memcache is available, this uses
    memcache as the backend. Otherwise, this uses :obj:`pickle` to cache
    the outputs in the local file system.

    Args:
      filename (:obj:`str`, optional): The file path to the cache file. This is
          used only when :obj:`pickle` is used as the backend.