docs: def get_versions(self):
  
  		'''
  		retrieves all versions of an object, and stores them at self.versions
  
  		Args:
  			None
  
  		Returns:
  			None: appends instances
  		'''
  
  		# get all versions
  		versions_response = self.repo.api.http_request('GET', '%s/fcr:versions' % self.uri)
  
  		# parse response
  		versions_graph = self.repo.api.parse_rdf_payload(versions_response.content, versions_response.headers)
  
  		# loop through fedora.hasVersion
  		for version_uri in versions_graph.objects(self.uri, self.rdf.prefixes.fedora.hasVersion):
  
  			# get label
  			version_label = versions_graph.value(version_uri, self.rdf.prefixes.fedora.hasVersionLabel, None).toPython()
  
  			# affix version
  			self._affix_version(version_uri, version_label)