How to parse list of tuples with behave

Question

How can I parse a list of tuples with behave? Tried looking at through the example here: https://behave.github.io/behave.example/datatype/cardinality_one_or_more.html but cannot figure it out. I originally tried using regex to locate the brackets but then figured there has to be a simpler built-in way of parsing a list of tuples

My scenario has this:

When I run the service "service" with input args [("21-01", "21-01")]

And the step function is

@when("I run the service {name} with input args {arg}")
def run_service(context, name, arg=None):
    context.service_result = wrapper.wrappers[name](context.workset.getID(), arg)

However when the service is actually run, the input arg is always one big string rather than a list of tuples:

class service(InheritedClass):
    def work(self, workset, *args):
        print args
        print args[0]
        print args[0][0]
        print type(args[0][0])

Where the output is

      ('[("21-01", "21-01")]',)
      [("21-01", "21-01")]
      [
      <type 'str'>