code: public static <T> Function<T, Void> function(Consumer<T> adaptee) {
          dbc.precondition(adaptee != null, "cannot adapt a null consumer");
          return first -> {
              adaptee.accept(first);
              return null;
          };
      }
docs: Adapts an consumer to a function.
  
  @param <T> the consumer parameter type
  @param adaptee the consumer to be adapted
  @return the adapted function