public Kv schema(String schema) {
        checkNotNull(schema);
        internalProperties.putString(TableFormatConstants.FORMAT_SCHEMA, schema);
        return this;
    }
Sets the format schema. Required if schema is not derived.

@param schema format schema string.
inlong-sort/sort-formats/format-row/format-kv/src/main/java/org/apache/inlong/sort/formats/kv/Kv.java