(jython/ python)Can't seem to get the image copy I made in jython outside of my def

Hi I have a single block of code for an excersize I'm trying to write that I can't figure out why the copied image is not callable outside of the definition. Also I don't understand why or what to put in the brackets of the definition, or why I would, as the excersize is asking me to have the definition title written exactly as I currently have it. Also, why would I use the statement "return" as shown in some other code examples I've seen?

Do you spot any redundancies too? =\

Here's the Code:

def makeCopyOfAPicture(picOriginal):
    source = pickAFile()
    picOriginal = makePicture(source)
    picWidth = getWidth(picOriginal)
    picHeight = getHeight(picOriginal)
    picCopy = makeEmptyPicture(picWidth, picHeight)
    targetX = 0
    for sourceX in range(0,getWidth(picOriginal)):
        targetY = 0
        for sourceY in range(0,getHeight(picOriginal)):
            color = getColor(getPixel(picOriginal,sourceX,sourceY))
            setColor(getPixel(picCopy, targetX, targetY), color)
            targetY = targetY + 1
        targetX = targetX + 1
    show(picOriginal)
    show(picCopy)
#   print(picCopy)
#   print(picOriginal)
    return picCopy

makeCopyOfAPicture(picOriginal)

TIA!