static IsNullConditional forField(FieldSpec field) {
        IsNullConditional cond = new IsNullConditional(field.camelCaseName());
        cond.nullableVersions(field.nullableVersions());
        return cond;
    }
For versions of a field that are nullable, IsNullCondition creates a null check.
generator/src/main/java/org/apache/kafka/message/IsNullConditional.java