code: private void tryDisposeAllOperators() throws Exception {
  		for (StreamOperator<?> operator : operatorChain.getAllOperators()) {
  			if (operator != null) {
  				operator.dispose();
  			}
  		}
  	}
docs: Execute {@link StreamOperator#dispose()} of each operator in the chain of this
  {@link StreamTask}. Disposing happens from <b>tail to head</b> operator in the chain.