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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:
 async def prover_get_credentials(wallet_handle: int, filter_json: str) -> str: """ Gets human readable credentials according to the filter. If filter is NULL, then all credentials are returned. Credentials can be filtered by tags created during saving of credential. NOTE: This method is deprecated because immediately returns all fetched credentials. Use <prover_search_credentials> to fetch records by small batches. :param wallet_handle: wallet handler (created by open_wallet). :param filter_json: filter for credentials { "schema_id": string, (Optional) "schema_issuer_did": string, (Optional) "schema_name": string, (Optional) "schema_version": string, (Optional) "issuer_did": string, (Optional) "cred_def_id": string, (Optional) } :return: credentials json [{ "referent": string, // cred_id in the wallet "attrs": {"key1":"raw_value1", "key2":"raw_value2"}, "schema_id": string, "cred_def_id": string, "rev_reg_id": Optional<string>, "cred_rev_id": Optional<string> }] """


    logger = logging.getLogger(__name__)
    logger.debug("prover_get_credentials: >>> wallet_handle: %r, filter_json: %r",
                 wallet_handle,
                 filter_json)

    if not hasattr(prover_get_credentials, "cb"):
        logger.debug("prover_get_credentials: Creating callback")
        prover_get_credentials.cb = create_cb(CFUNCTYPE(None, c_int32, c_int32, c_char_p))

    c_wallet_handle = c_int32(wallet_handle)
    c_filter_json = c_char_p(filter_json.encode('utf-8'))

    credentials_json = await do_call('indy_prover_get_credentials',
                                     c_wallet_handle,
                                     c_filter_json,
                                     prover_get_credentials.cb)

    res = credentials_json.decode()
    logger.debug("prover_get_credentials: <<< res: %r", res)
    return res