src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> fromIterable(Iterable<? extends T> source) {
        ObjectHelper.requireNonNull(source, "source is null");
        return RxJavaPlugins.onAssembly(new FlowableFromIterable<T>(source));
    }
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> fromIterable(Iterable<? extends T> source) {
        ObjectHelper.requireNonNull(source, "source is null");
        return RxJavaPlugins.onAssembly(new FlowableFromIterable<T>(source));
    }
Converts an {@link Iterable} sequence into a Publisher that emits the items in the sequence.
<p>
<img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/from.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream and iterates the given {@code iterable}
on demand (i.e., when requested).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code fromIterable} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param source
the source {@link Iterable} sequence
@param <T>
the type of items in the {@link Iterable} sequence and the type of items to be emitted by the
resulting Publisher
@return a Flowable that emits each item in the source {@link Iterable} sequence
@see <a href="http://reactivex.io/documentation/operators/from.html">ReactiveX operators documentation: From</a>