code: private void checkKey(final byte[] key) {
  		if (theBinaryKey.get() != null) {
  			verifyKey(key);
  		} else {
  			boolean success = theBinaryKey.compareAndSet(null, key);
  			if (!success) {
  				// someone already beat us to it. that's fine, just verify
  				// that the key is the same
  				verifyKey(key);
  			} else {
  				pipelined(key);
  			}
  		}
  	}
docs: Checks that a pipeline is associated with a single key. Binary keys do not
  support hashtags.
  
  @param key