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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def init_app(self, app):
 """This callback can be used to initialize an application for the use with this database setup. Never use a database in the context of an application not initialized that way or connections will leak. """

        if (
            'SQLALCHEMY_DATABASE_URI' not in app.config and
            'SQLALCHEMY_BINDS' not in app.config
        ):
            warnings.warn(
                'Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. '
                'Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".'
            )

        app.config.setdefault('SQLALCHEMY_DATABASE_URI', 'sqlite:///:memory:')
        app.config.setdefault('SQLALCHEMY_BINDS', None)
        app.config.setdefault('SQLALCHEMY_NATIVE_UNICODE', None)
        app.config.setdefault('SQLALCHEMY_ECHO', False)
        app.config.setdefault('SQLALCHEMY_RECORD_QUERIES', None)
        app.config.setdefault('SQLALCHEMY_POOL_SIZE', None)
        app.config.setdefault('SQLALCHEMY_POOL_TIMEOUT', None)
        app.config.setdefault('SQLALCHEMY_POOL_RECYCLE', None)
        app.config.setdefault('SQLALCHEMY_MAX_OVERFLOW', None)
        app.config.setdefault('SQLALCHEMY_COMMIT_ON_TEARDOWN', False)
        track_modifications = app.config.setdefault(
            'SQLALCHEMY_TRACK_MODIFICATIONS', None
        )
        app.config.setdefault('SQLALCHEMY_ENGINE_OPTIONS', {})

        if track_modifications is None:
            warnings.warn(FSADeprecationWarning(
                'SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and '
                'will be disabled by default in the future.  Set it to True '
                'or False to suppress this warning.'
            ))

        # Deprecation warnings for config keys that should be replaced by SQLALCHEMY_ENGINE_OPTIONS.
        utils.engine_config_warning(app.config, '3.0', 'SQLALCHEMY_POOL_SIZE', 'pool_size')
        utils.engine_config_warning(app.config, '3.0', 'SQLALCHEMY_POOL_TIMEOUT', 'pool_timeout')
        utils.engine_config_warning(app.config, '3.0', 'SQLALCHEMY_POOL_RECYCLE', 'pool_recycle')
        utils.engine_config_warning(app.config, '3.0', 'SQLALCHEMY_MAX_OVERFLOW', 'max_overflow')

        app.extensions['sqlalchemy'] = _SQLAlchemyState(self)

        @app.teardown_appcontext
        def shutdown_session(response_or_exc):
            if app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN']:
                if response_or_exc is None:
                    self.session.commit()

            self.session.remove()
            return response_or_exc