How can I create a rule in Blazegraph with NOT EXISTS constraint?

Question

This question is related to the Blazegraph Java samples. I want to create a rule with a SPARQL NOT EXISTS clause. This Blazegraph rule sample provides a constraint clause that checks for IsLiteral(). I want to implement a rule that provides the following functionality:

?a rdf:type xyz:T .
filter(not exits(?a xyz:p ?o)) .
->
?a xyz:q xyz:T

I checked for suitable classes in: com.bigdata.rdf.internal.constraints and can't find a BOp class that supports EXIST (and MINUS). I found a NOT operator NotBOp().

Here is the constraint that I want to create with a fictitious ExistsBOp function:

new IConstraint[] { // constraints
    // you can use SPARQL value expression bops in inference by wrapping them with an InferenceBVE
    Constraint.wrap(new InferenceBVE(new NotBOp(new ExistsBOp(var("a"), vocab.getConstant(XYZ.q), vocab.getConstant(XYZ.T))))
}

Is there another way to achieve the constraint?