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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 isDirty(self, CachableItem):
 """True if cached information requires update for ICachableItem"""

        _cachedItem = self.get(CachableItem)
        if not _cachedItem:
            return True
        _newCacheItem = self.mapper.get(CachableItem)
        return False if _cachedItem == _newCacheItem else True