code: def keepalive(nurse, *patients):
      
      if DISABLED:
          return
      if hashable(nurse):
          hashable_patients = []
          for p in patients:
              if hashable(p):
                  log.debug("Keeping {0} alive for lifetime of {1}".format(p, nurse))
                  hashable_patients.append(p)
              else:
                  log.warning("Unable to keep unhashable object {0} "
                              "alive for lifetime of {1}".format(p, nurse))
          KEEPALIVE.setdefault(nurse, set()).update(hashable_patients)
      else:
          log.warning("Unable to keep objects alive for lifetime of "
                      "unhashable object {0}".format(nurse))
docs: Keep ``patients`` alive at least as long as ``nurse`` is around using a
      ``WeakKeyDictionary``.