calling on a method from one class into another class which is not a child

[NABA]

I have a class called World, another one called Fish. Fish is not a child of World, and I want to call the method getMaxX() and getMaxY() into the Fish class, but I get attribute errors. How Can I Call getMaxX() and getMaxY() from World class into Fish class?

class World:
    def __init__(self, mX, mY):
        self.__maxX = mX
        self.__maxY = mY
        self.__thingList = []
        self.__grid = []
.....

    def getMaxX(self):
        return self.__maxX

    def getMaxY(self):
        return self.__maxY


#Now here is the Fish class

class Fish(LifeForm):
    def __init__(self):
        super().__init__("Fish.gif")
        
        self.__breedTick = 0
        self.__starveTick = 0
   ...

    def liveALittle(self):
        offsetList = [(-1,1), (0,1), (1,1),
                      (-1,0),        (1,0),
                      (-1,-1),(0,-1),(1,-1)]
        adjFish = 0  #count adjacent Fish
        for offset in offsetList:
            newX = self.getX() + offset[0]
            newY = self.getY() + offset[1]
            if 0 <= newX < ??????????????? and \
                  0 <= newY <????????????????????):
                if (not World.emptyLocation(newX, newY)) and \
                    isinstance(World.lookAtLocation(newX, newY), Fish):
                    adjFish = adjFish + 1

        if adjFish >= 2:   #if 2 or more adjacent Fish, die
            World.delThing()
        else:
            self.__breedTick = self.__breedTick + 1
            if self.__breedTick >= 12:  #if alive 12 or more ticks, breed
                self.tryToBreed()

...

What should go there instead of ??? I tried World.getMaxX(), self.__world.getMaxX(), etc. Nothing worked. I'm getting an attribute error saying the Fish doesn't have any world attribute or the missing positional argument:self error.