How to check if a dictionary is empty?

I am trying to check if a dictionary is empty but it doesn't behave properly. It just skips it and displays ONLINE without anything aside from the display the message. Any ideas why ?

def isEmpty(self, dictionary):
    for element in dictionary:
        if element:
            return True
        return False

def onMessage(self, socket, message):
    if self.isEmpty(self.users) == False:
        socket.send("Nobody is online, please use REGISTER command" \
                 " in order to register into the server")
    else:
        socket.send("ONLINE " + ' ' .join(self.users.keys()))