Problem with Monster game

So I typed the game in and thought I had it all correct. But when I run it in Terminal, it gives me "NameError: name 'get_next_monster' is not defined". Even though get_next_monster is the next thing in the file!

I know that order doesn't matter, unlike some languages.

I even tried cutting and pasting the rest of the code (what's not relevant to the problem) to another file just to eliminate problems as much as possible.

I also temporarily redefined the get_next_monster() method to simply print out a message, again to reduce any code that might be complicating things.

I have python 3.4 on my Mac (OS X 10.9.5), though I'm not sure if that has anything to do with it.

I just do not for the life of me understand what is wrong with this that is causing it to throw up errors. I thought I had typed it (well, other than what I changed afterwards) correctly, but it just refuses to work and keeps giving me the same error. Maybe it's something stupid and simple that I'm overlooking.

Thanks!

import sys
from character import Character
from monster import Dragon
from monster import Goblin
from monster import Troll


class Game:

    def setup(self):
        self.player = Character()
        self.monsters = [
            Goblin(), 
            Troll(), 
            Dragon() 
        ]
        self.monster = get_next_monster()

    def get_next_monster(self):
        print ('the next monster is up!')

    def __init__(self):
        self.setup()

Game()