code: def exclusive(via=threading.Lock):
      
      def make_exclusive(fnc):
          fnc_guard = via()
  
          @functools.wraps(fnc)
          def exclusive_call(*args, **kwargs):
              if fnc_guard.acquire(blocking=False):
                  try:
                      return fnc(*args, **kwargs)
                  finally:
                      fnc_guard.release()
              else:
                  raise RuntimeError('exclusive call to %s violated')
          return exclusive_call
      return make_exclusive
docs: Mark a callable as exclusive
  
      :param via: factory for a Lock to guard the callable
  
      Guards the callable against being entered again before completion.
      Explicitly raises a :py:exc:`RuntimeError` on violation.
  
      :note: If applied to a method, it is exclusive across all instances.