Initializes the Flask application with this extension. It grabs
        the necessary configuration values from ``app.config``, those being
        HASHING_METHOD and HASHING_ROUNDS. HASHING_METHOD defaults to ``sha256``
        but can be any one of ``hashlib.algorithms``. HASHING_ROUNDS specifies
        the number of times to hash the input with the specified algorithm.
        This defaults to 1.

        :param app: Flask application object

def init_app(self, app):
        '''Initializes the Flask application with this extension. It grabs
        the necessary configuration values from ``app.config``, those being
        HASHING_METHOD and HASHING_ROUNDS. HASHING_METHOD defaults to ``sha256``
        but can be any one of ``hashlib.algorithms``. HASHING_ROUNDS specifies
        the number of times to hash the input with the specified algorithm.
        This defaults to 1.

        :param app: Flask application object
        '''
        self.algorithm = app.config.get('HASHING_METHOD', 'sha256')
        if self.algorithm not in algs:
            raise ValueError('{} not one of {}'.format(self.algorithm, algs))
        self.rounds = app.config.get('HASHING_ROUNDS', 1)
        if not isinstance(self.rounds, int):
            raise TypeError('HASHING_ROUNDS must be type int')