How to use capture groups in vim to move function arguments to the previous line?

I have a bunch of python functions being called like this:

function1([arg1, arg2, arg3])
function2([arg1, arg2, arg3])
...

And I'm wondering if there is a capture group that I can use to do something like this:

args = [arg1, arg2, arg3]
function(args)
args = [arg1, arg2, arg3]
function(args)    
...

Or (even better but not necessary):

args1 = [arg1, arg2, arg3]
function(args)
args2 = [arg1, arg2, arg3]
function(args)

This is all I've tried so far :s/function[0-9](.)/args = $1 nfunction(args)/g