public Schema schema() {
            SchemaBuilder builder = SchemaBuilder.type(knownType);
            if (optional) {
                builder.optional();
            }
            return builder.schema();
        }
Merge two schemas to a common schema which can represent values from both input schemas.
@param previous One Schema, non-null
@param newSchema Another schema, non-null
@return A schema that is a superset of both input schemas, or null if no common schema is found.
connect/api/src/main/java/org/apache/kafka/connect/data/Values.java