code: def _add_assertion_provenance(
              self,
              assoc_id,
              evidence_line_bnode
      ):
          
          provenance_model = Provenance(self.graph)
          model = Model(self.graph)
          assertion_bnode = self.make_id(
              "assertion{0}{1}".format(assoc_id, self.localtt['IMPC']), '_')
  
          model.addIndividualToGraph(assertion_bnode, None, self.globaltt['assertion'])
  
          provenance_model.add_assertion(
              assertion_bnode, self.localtt['IMPC'],
              'International Mouse Phenotyping Consortium')
  
          self.graph.addTriple(
              assoc_id, self.globaltt['proposition_asserted_in'], assertion_bnode)
  
          self.graph.addTriple(
              assertion_bnode,
              self.resolve('is_assertion_supported_by_evidence'),  # "SEPIO:0000111"
              evidence_line_bnode)
  
          return
docs: Add assertion level provenance, currently always IMPC
          :param assoc_id:
          :param evidence_line_bnode:
          :return: