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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 output_keys(self, source_keys):
 """ Given input chunk keys, compute what keys will be needed to put the result into the result array. As an example of where this gets used - when we aggregate on a particular axis, the source keys may be ``(0:2, None:None)``, but for an aggregation on axis 0, they would result in target values on dimension 2 only and so be ``(None: None, )``. """

        keys = list(source_keys)
        # Remove the aggregated axis from the keys.
        del keys[self.axis]
        return tuple(keys)