How do I do transparent vendor mixins in Stylus when the mixin function is an argument?

Making a mixin for properties like border-radius is easy:

vendor(name, args)
    -webkit-{name} args
    -moz-{name} args
    -ie-{name} args
    -o-{name} args
    {name} args

border-radius()
    vendor('border-radius', arguments)

#test
    border-radius 5px

But what if I want to create a transparent vendor mixin for linear-gradient? Unlike border-radius, linear-gradient is not a property but an argument, e.g.

#test
    background-image linear-gradient(top, #f00 0%, #00f 100%)

I'm thinking I have to create a mixin called background-image and check if the first argument is linear-gradient. Is Stylus capable of such advanced logic? If so, how can I accomplish what I'm trying to do?

Thanks for any help on the matter.