<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def init_app(self, app, sqla, namespace='api', route_prefix='/api'):
 """ Initialize the adapter if it hasn't already been initialized. :param app: Flask application :param sqla: Flask-SQLAlchemy instance :param namespace: Prefixes all generated routes :param route_prefix: The base path for the generated routes """

        self.app = app
        self.sqla = sqla

        self._setup_adapter(namespace, route_prefix)