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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 clear_cache(self):
 """Clear the raw packet cache for the field and all its subfields"""

        self.raw_packet_cache = None
        for _, fval in six.iteritems(self.fields):
            if isinstance(fval, Packet):
                fval.clear_cache()
        self.payload.clear_cache()