Create an @authenticated decorator that only allows the function to run is user1 has 'valid' set to True:

user1 = {
'name': 'Sorna',
'valid': True
}

def authenticated(fn):
def wrapper(*args, **kwargs):
if args[0]['valid']:
return fn(*args, **kwargs)
return wrapper

@authenticated
def message_friends(user):
print('message has been sent')

message_friends(user1)