public MetadataResultSet transform(String columnLabel, ClickHouseColumn column, UnaryOperator<String> transformer) {
        if (columnLabel != null && transformer != null) {
            columnTransformers.put(columnLabel.toUpperCase(), transformer);
        }
        overridingSchemaAdaptor.setOverriddenColumn(overridingSchemaAdaptor.nameToIndex(columnLabel), column);
        return this;
    }
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