code: def update_release_definition(self, release_definition, project):
          
          route_values = {}
          if project is not None:
              route_values['project'] = self._serialize.url('project', project, 'str')
          content = self._serialize.body(release_definition, 'ReleaseDefinition')
          response = self._send(http_method='PUT',
                                location_id='d8f96f24-8ea7-4cb6-baab-2df8fc515665',
                                version='5.1-preview.3',
                                route_values=route_values,
                                content=content)
          return self._deserialize('ReleaseDefinition', response)
docs: UpdateReleaseDefinition.
          [Preview API] Update a release definition.
          :param :class:`<ReleaseDefinition> <azure.devops.v5_1.release.models.ReleaseDefinition>` release_definition: Release definition object to update.
          :param str project: Project ID or project name
          :rtype: :class:`<ReleaseDefinition> <azure.devops.v5_1.release.models.ReleaseDefinition>`