How to update RDF graph by instantiating the variables existing in triples with values?

I have a knowledge base that looks as follows:

@prefix ex: <http://example.org/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

ex:a a ex:C .

ex:C rdfs:subClassOf ex:D .

ex:D rdfs:subClassOf ex:E .

And I have the following rule:

s rdf.type X, X rdfs.subClassOf Y -> s rdf.type Y

where the triple s type Y is a consequent and the triples s type X, X subClassOf Y are antecedents.

My goal

I have the consequent a type E. I have to pattern match the consequent with the rule given above and find the antecedents. In this example, if I pattern match the consequent a type E, then the antecedents should look like this:

a type ?X, ?X subClassOf E.

In this case, I try to make a graph for antecedents where it looks like the following:

@prefix ex: <http://example.org/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

ex:a rdf:type _:X .

_:X rdfs:subClassOf ex:E .

Then I check if it possible to pattern match the antecedents with any element of KB (by iteratively going through the antecedents). In this example, it is possible to pattern match the first triple ex.a rdf.type ?X because a type ?X is pattern matched with the element of the KB a type C. So, ?X = C. Then I instantiate all ?X for all triples in the antecedents with C where the triples should be updated this way: a type C, C subClassOf E. Therefore, my updated antecedent graph should look like the following:

@prefix ex: <http://example.org/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

ex:a rdf:type ex:C .

ex:C rdfs:subClassOf ex:E .

My code so far

I implemented the Python code to create the antecedent graph the following way:

consequent = (ex.a, rdf.type, ex.E)

# Create a new RDF graph for the antecedents
antecedent_graph = Graph()

def serialize_antecedent_graph():
    # antecedent_graph.serialize() returns a string
    print(antecedent_graph.serialize(format='turtle'))

antecedent_graph.bind('ex', ex)
antecedent_graph.bind('rdf', rdf)
antecedent_graph.bind('rdfs', rdfs)

# --- R5 ---
if (consequent[1].eq(URIRef("http://www.w3.org/1999/02/22-rdf-syntax-ns#type"))):
  X = BNode()
  antecedent_graph.add((consequent[0], rdf.type, X))
  antecedent_graph.add((X, rdfs.subClassOf, consequent[2]))

serialize_antecedent_graph()

My questions

1. How can I update my antecedent graph in the way that is shown above?

2. Currently I'm introducing variable in my antecedent graph the following way:

X = BNode()
antecedent_graph.add((consequent[0], rdf.type, X))

Is this approach correct? Is there an efficient and alternative way to do it?

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