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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 toProtocolElement(self):
 """ Returns the GA4GH protocol representation of this Reference. """

        reference = protocol.Reference()
        reference.id = self.getId()
        reference.is_derived = self.getIsDerived()
        reference.length = self.getLength()
        reference.md5checksum = self.getMd5Checksum()
        reference.name = self.getName()
        if self.getSpecies():
            term = protocol.fromJson(
                json.dumps(self.getSpecies()), protocol.OntologyTerm)
            reference.species.term_id = term.term_id
            reference.species.term = term.term
        reference.source_accessions.extend(self.getSourceAccessions())
        reference.source_divergence = pb.int(self.getSourceDivergence())
        reference.source_uri = self.getSourceUri()
        self.serializeAttributes(reference)
        return reference