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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def process_file(self,filename=None, format=None):
 """ Parse a file into an ontology object, using rdflib """

        rdfgraph = rdflib.Graph()
        if format is None:
            if filename.endswith(".ttl"):
                format='turtle'
            elif filename.endswith(".rdf"):
                format='xml'
        rdfgraph.parse(filename, format=format)
        return self.process_rdfgraph(rdfgraph)