`<attribute>` element

<attribute> element defines an attribute for a token or a card

Attributes requires the attribute @name. It can have any given name and will be used to call the attribute.

An attribute from a smart contract function call

    <ts:attribute name="balance">
        <ts:origins>
            <ethereum:call function="balanceOf" as="uint">
                <ts:data><ts:address ref="ownerAddress"/></ts:data>
            </ethereum:call>
        </ts:origins>
    </ts:attribute>