initialize pre request hooks

def _init_request_hooks(self):
        """ initialize pre request hooks"""
        for method_type in ('pre', 'post'):
            for method in _METHODS:
                event = getattr(self.app, 'on_' + method_type + '_' + method)
                event_hook = getattr(hooks, method_type + '_' + method)
                event += event_hook