def combineIndicatorMaps(maps, squareSize, combinationFunction):
    """Puts many indicator maps together 
    (averaging the values in each cell 
    if more than one maps has a value)"""
    indicatorMap = {}
    for m in maps:
        for k, v in m.items():
            if k in indicatorMap:
                indicatorMap[k].append(v)
            else:
                indicatorMap[k] = [v]
    for k in indicatorMap:
        indicatorMap[k] = combinationFunction(indicatorMap[k])
    return indicatorMap
