Method from

guava/src/com/google/common/collect/FluentIterable.java:139–148

Returns a fluent iterable that wraps {@code iterable}, or {@code iterable} itself if it is already a {@code FluentIterable}. <p><b>{@code Stream} equivalent:</b> {@link Collection#stream} if {@code iterable} is a {@link Collection}; {@link Streams#stream(Iterable)} otherwise.

(Iterable<E> iterable)

   * Collection}; {@link Streams#stream(Iterable)} otherwise.
   */
  public static <E extends @Nullable Object> FluentIterable<E> from(Iterable<E> iterable) {
    return (iterable instanceof FluentIterable)
        ? (FluentIterable<E>) iterable
        : new FluentIterable<E>(iterable) {
          @Override
          public Iterator<E> iterator() {
            return iterable.iterator();
          }
        };
  }

  /**
   * Returns a fluent iterable containing {@code elements} in the specified order.