    /**
     * @notice Checks if a specific voter has already voted for a given art piece.
     * @param pieceId The ID of the art piece.
     * @param voter The address of the voter.
     * @return A boolean indicating if the voter has voted for the art piece.
     */
    function hasVoted(uint256 pieceId, address voter) external view returns (bool) {
        return votes[pieceId][voter].voterAddress != address(0);
    }
-        require(!(votes[pieceId][voter].voterAddress != address(0)), "Already voted");
+        require(!(hasVoted(pieceId, voter)), "Already voted");
