@Override
    public Set<Class<? extends VerificationStrategy>> applyPost() {
        return Collections.singleton(ComputerVerificationStrategy.class);
    }
Detects steps marked with {@link Mutating} and throws an {@link IllegalStateException} if one is found.

@author Marko A. Rodriguez (http://markorodriguez.com)
@example <pre>
__.out().addE()                 // throws an VerificationException
__.addV()                       // throws an VerificationException
__.property(key,value)          // throws an VerificationException
__.out().drop()                 // throws an VerificationException
</pre>
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/verification/ReadOnlyStrategy.java