Not being able to retrieve preview code

[achru]

Which SDK version are you using?

v0.13

What's the issue?

When trying to get the preview I am getting a Class object with no preview code.

Steps/Sample code to reproduce the issue

calling previews on created creative like so
FacebookAds::AdCreative.get(23851059200310039).previews(ad_format: "DESKTOP_FEED_STANDARD")

Observed Results:

 @name=:previews,
 @node=#<FacebookAds::AdCreative {:id=>"23851059200310039"}>,
 @options={:ad_format=>"DESKTOP_FEED_STANDARD"},
 @should_delegate=false>```

#### Expected Results:
Getting preview iframe code