} else if (FlowSpecification.class.isAssignableFrom(clz)) {
verifiers.put(clz, new FlowVerification());
} else if (ProgramSpecification.class.isAssignableFrom(clz)) {
verifiers.put(clz, createProgramVerifier((Class<ProgramSpecification>) clz));
} else if (DatasetCreationSpec.class.isAssignableFrom(clz)) {
verifiers.put(clz, new DatasetCreationSpecVerifier());
}
return (Verifier<T>) verifiers.get(clz);
}