public void setImpression(java.util.Collection<String> impression) {
        if (impression == null) {
            this.impression = null;
            return;
        }

        this.impression = new java.util.ArrayList<String>(impression);
    }
<p>
A list of item IDs that represents the sequence of items you have shown the user. For example,
<code>["itemId1", "itemId2", "itemId3"]</code>. Provide a list of items to manually record impressions data for
an event. For more information on recording impressions data, see <a href=
"https://docs.aws.amazon.com/personalize/latest/dg/recording-events.html#putevents-including-impressions-data"
>Recording impressions data</a>.
</p>

@param impression
       A list of item IDs that represents the sequence of items you have shown the user. For example,
       <code>["itemId1", "itemId2", "itemId3"]</code>. Provide a list of items to manually record impressions
       data for an event. For more information on recording impressions data, see <a href=
       "https://docs.aws.amazon.com/personalize/latest/dg/recording-events.html#putevents-including-impressions-data"
       >Recording impressions data</a>.
aws-java-sdk-personalizeevents/src/main/java/com/amazonaws/services/personalizeevents/model/Event.java