docs: def updateSystemMetadataResponse(self, pid, sysmeta_pyxb, vendorSpecific=None):
          """MNStorage.updateSystemMetadata(session, pid, sysmeta) → boolean
          http://jenkins-1.dataone.org/documentation/unstable/API-Documentation-
          development/apis/MN_APIs.html#MNStorage.updateSystemMetadata.
  
          Args:
            pid:
            sysmeta_pyxb:
            vendorSpecific:
  
          Returns:
  
          """
          mmp_dict = {
              'pid': pid.encode('utf-8'),
              'sysmeta': ('sysmeta.xml', sysmeta_pyxb.toxml('utf-8')),
          }
          return self.PUT('meta', fields=mmp_dict, headers=vendorSpecific)