How do you properly use flask RequestParser and swagger-ui with multiple params of the same name?

Question

I want to create a rest endpoint that allows multiple params of the same name, i.e. /api?param=a&param=b

I am using flask for the implementation and swagger-ui to create a nice ui where you can test the rest call. Here is what I have:

from flask.ext.restful.reqparse import RequestParser
parser = RequestParser()
parser.add_argument('param', type=str, location='args', action='append')

class Foo(Resource):
    @swagger.operation(
        parameters=[
            {
                "allowMultiple": True,
                "dataType": "string",
                "description": "Params(s)",
                "name": "param",
                "paramType": "query",
                "required": False
            }
        ]
    )
    def get(self):
        args = parser.parse_args()
        print args['param']

Problem 1: in the swagger-ui there is only one text field for the parameter that is supposed to allow multiple values. Problem 2: RequestParser turns the parameter into a List. So if I specify a comma separated list for instance in the swagger-ui, it will print ['value1,value2,value3'].

How can I specify a comma separated list in the ui or have multiple input fields? When the args are parsed it should be a List argument with multiple entries.