Types.ps1xml

<?xml version="1.0" encoding="utf-8" ?>
<Types>
    <Type>
        <Name>Amazon.EC2.Model.Reservation</Name>
        <Members>
            <ScriptProperty>
                <Name>InstanceId</Name>
                <GetScriptBlock>$this.Instances[0].InstanceId</GetScriptBlock>
            </ScriptProperty>
        </Members>
    </Type>
</Types>