renderer.py

class Renderer(object):
    def __init__(self, info):
        pass

    def __call__(self, value, system):
        ''' value bertipe DataResponse '''
        request = system.get('request')
        if request is not None:
            response = request.response
            ct = response.content_type
            if ct == response.default_content_type:
                response.content_type = 'text/csv'
        return str(value)