How to yield a nested IENumerable?
<p>I know how to yield values in a method with return value <code>IENumerable</code></p>

<pre><code>public IEnumerable&lt;int&gt; GetDigits()
{
    yield return 1;
    yield return 1;
    yield return 1;
}
</code></pre>

<p>but how is the correct Syntax for a nested <code>IEnumerable&lt;IEnumerable&lt;int&gt;&gt;</code>?</p>

<pre><code>public IEnumerable&lt;IEnumerable&lt;int&gt;&gt; GetNestedDigits()
{
    yield return yield return 1; //??
}
</code></pre>