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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 prune_creds_json(creds: dict, cred_ids: set) -> str: """ Strip all creds out of the input json structure that do not match any of the input credential identifiers. :param creds: indy-sdk creds structure :param cred_ids: the set of credential identifiers of interest :return: the reduced creds json """


    rv = deepcopy(creds)
    for key in ('attrs', 'predicates'):
        for attr_uuid, creds_by_uuid in rv[key].items():
            rv[key][attr_uuid] = [cred for cred in creds_by_uuid if cred['cred_info']['referent'] in cred_ids]

        empties = [attr_uuid for attr_uuid in rv[key] if not rv[key][attr_uuid]]
        for attr_uuid in empties:
            del rv[key][attr_uuid]

    return json.dumps(rv)