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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 updateItem(self, instance, subKey, value):
 """Updates a child value. Must be called before the update has actually occurred."""

    instanceId = statsId(instance)

    container = _Stats.getContainerForObject(instanceId)
    self._aggregate(instanceId, container, value, subKey)