docs: def fixity(self, response_format=None):
  
  		'''
  		Issues fixity check, return parsed graph
  
  		Args:
  			None
  
  		Returns:
  			(dict): ('verdict':(bool): verdict of fixity check, 'premis_graph':(rdflib.Graph): parsed PREMIS graph from check)
  		'''
  
  		# if no response_format, use default
  		if not response_format:
  			response_format = self.repo.default_serialization
  
  		# issue GET request for fixity check
  		response = self.repo.api.http_request('GET', '%s/fcr:fixity' % self.uri)
  
  		# parse
  		fixity_graph = self.repo.api.parse_rdf_payload(response.content, response.headers)
  
  		# determine verdict
  		for outcome in fixity_graph.objects(None, self.rdf.prefixes.premis.hasEventOutcome):
  			if outcome.toPython() == 'SUCCESS':
  				verdict = True
  			else:
  				verdict = False
  
  		return {
  			'verdict':verdict,
  			'premis_graph':fixity_graph
  		}