in java/avro-converter/src/main/java/com/microsoft/azure/schemaregistry/kafka/connect/avro/AvroConverterUtils.java [1381:1384]
private static boolean isEnumSchema(Schema schema) {
return schema.type() == Schema.Type.STRING && schema.parameters() != null
&& schema.parameters().containsKey(AVRO_TYPE_ENUM);
}