How to use the twitterapi._FileCache function in TwitterAPI

def __init__(self,
               username=None,
               password=None,
               input_encoding=None,
               request_headers=None):
    '''Instantiate a new twitterapi.Api object.

    Args:
      username: The username of the twitter account.  [optional]
      password: The password for the twitter account. [optional]
      input_encoding: The encoding used to encode input strings. [optional]
      request_header: A dictionary of additional HTTP request headers. [optional]
    '''
    self._cache = _FileCache()
    self._urllib = urllib2
    self._cache_timeout = Api.DEFAULT_CACHE_TIMEOUT
    self._InitializeRequestHeaders(request_headers)
    self._InitializeUserAgent()
    self._InitializeDefaultParameters()
    self._input_encoding = input_encoding
    self.SetCredentials(username, password)