@Override
    public String getString(String columnLabel) throws SQLException {
        String value = super.getString(columnLabel);
        UnaryOperator<String> transformer = columnTransformers.get(columnLabel.toUpperCase());
        if (transformer != null && value != null) {
            return transformer.apply(value);
        }
        return value;
    }
Registers a transformer function for a given column.
The transformer takes the original String value and returns a new String.

@param columnLabel The name of the column (case-insensitive).
@param transformer The function that transforms the value.
jdbc-v2/src/main/java/com/clickhouse/jdbc/internal/MetadataResultSet.java