function isTransferAuthorized(address _from, address _to) public view returns (bool) {
        
        
        

        uint expiry = transferAuthorizations.get(_from, _to);
        uint globalExpiry = transferAuthorizations.get(_from, 0);
        if(globalExpiry > expiry) {
            expiry = globalExpiry;
        }

        return expiry > block.timestamp;
    }