static SchemaBuilder mapWithNullValues(Schema keySchema) {
        SchemaBuilder result = new SchemaBuilder(Type.MAP);
        result.keySchema = keySchema;
        return result;
    }
@param keySchema the schema for keys in the map
@param valueSchema the schema for values in the map
@return a new {@link Schema.Type#MAP} SchemaBuilder
connect/api/src/main/java/org/apache/kafka/connect/data/SchemaBuilder.java