How to get SimplePie fetch_feed without stripping iframe code?

I’m grabbing a remote feed in my plugin and some entries have iframe code I want to keep. However, SimplePie fetch_feed keeps stripping it out. Here is my code and what I’ve tried already:

kses_remove_filters(); # remove kses filters but SimplePie strips codes anyway
$rss = fetch_feed( 'http://www.someblog.com/feed/' );
$rss_items = $rss->get_items( 0, 2 );  # get two entries for this example
foreach ( $rss_items as $item ) {
    # just dump to screen:
    echo "<div id='message' class='updated'><p>" .  $item->get_content() . "</p></div>";
}
kses_init_filters(); # remove kses filters but SimplePie strips codes anyway


# also tried adding iframe to kses_allowed_html filter:
function se87359_add_filter( &$feed, $url ) {
    add_filter('wp_kses_allowed_html', 'se87359_add_allowed_tags');
}
add_filter( 'wp_feed_options', 'se87359_add_filter', 10, 2 );
function se87359_add_allowed_tags($tags) {
    // Ensure we remove it so it doesn't run on anything else
    remove_filter('wp_kses_allowed_html', 'se87359_add_allowed_tags');
    $tags['iframe'] = array(
    'src' => true,
    'width' => true,
    'height' => true,
    'class' => true,
    'frameborder' => true,
    'webkitAllowFullScreen' => true,
    'mozallowfullscreen' => true,
    'allowFullScreen' => true
    );
    return $tags;
}

# also made sure not to cache the feed (for testing only):
function do_not_cache_feeds(&$feed) {
    $feed->enable_cache(false);
}
add_action( 'wp_feed_options', 'do_not_cache_feeds' );

# in case above doesn't work, set transient lifetime to 1 second:
add_filter( 'wp_feed_cache_transient_lifetime', create_function( '$a', 'return 1;' ) );

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