code: public void push(final K key, final V value) {
          Optional.ofNullable(registered.get(key))
                  .ifPresent(a -> a.offer(value));
      }
docs: Push a single value synchronously into the Adapter identified by the supplied Key,
  if it exists
  
  <pre>
  {@code
  
  Pipes<String,String> pipes = Pipes.of();
  pipes.register("hello", new Queue<String>());
  
  pipes.push("hello", "world");
  
  on another thread
  pipes.reactiveSeq("hello")
  .getValue()
  .forEach(System.out::println);
  
  }
  </pre>
  
  @param key Adapter key
  @param value Value to push to Adapter