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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def ss_to_xy(s: str):
 """convert spreadsheet coordinates to zero-index xy coordinates. return None if input is invalid"""

    result = re.match(r'\$*([A-Z]+)\$*([0-9]+)', s, re.I)
    if result == None:
        return None
    xstring = result.group(1).upper()
    multiplier = 1
    x = 0
    for i in xstring:
        x = x * multiplier + (ord(i) - 64)
        multiplier = multiplier * 26
    x = x - 1
    y = int(result.group(2))-1
    return (x,y)