code: @Nullable
  	public O peek() {
  		if (!isTerminated()) {
  			return null;
  		}
  
  		if (value != null) {
  			return value;
  		}
  
  		if (error != null) {
  			RuntimeException re = Exceptions.propagate(error);
  			re = Exceptions.addSuppressed(re, new Exception("Mono#peek terminated with an error"));
  			throw re;
  		}
  
  		return null;
  	}
docs: Returns the value that completed this {@link MonoProcessor}. Returns {@code null} if the {@link MonoProcessor} has not been completed. If the
  {@link MonoProcessor} is completed with an error a RuntimeException that wraps the error is thrown.
  
  @return the value that completed the {@link MonoProcessor}, or {@code null} if it has not been completed
  
  @throws RuntimeException if the {@link MonoProcessor} was completed with an error