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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 pack_header_for_user( self, user, override_access_lifespan=None, override_refresh_lifespan=None, **custom_claims ):
 """ Encodes a jwt token and packages it into a header dict for a given user :param: user: The user to package the header for :param: override_access_lifespan: Override's the instance's access lifespan to set a custom duration after which the new token's accessability will expire. May not exceed the refresh_lifespan :param: override_refresh_lifespan: Override's the instance's refresh lifespan to set a custom duration after which the new token's refreshability will expire. :param: custom_claims: Additional claims that should be packed in the payload. Note that any claims supplied here must be JSON compatible types """

        token = self.encode_jwt_token(
            user,
            override_access_lifespan=override_access_lifespan,
            override_refresh_lifespan=override_refresh_lifespan,
            **custom_claims
        )
        return {self.header_name: self.header_type + ' ' + token}