@Override
    public Field field(String fieldName) {
        if (type != Type.STRUCT)
            throw new DataException("Cannot look up fields on non-struct type");
        return fields.get(fieldName);
    }
Get the list of fields for this Schema. Throws a {@link DataException} if this schema is not a {@link Schema.Type#STRUCT}.
@return the list of fields for this Schema
connect/api/src/main/java/org/apache/kafka/connect/data/SchemaBuilder.java