@staticmethod
def get_url_adapter(step_key, adapter_id, back_page=None):
    """
        Compute the URLs for a given adapter. 
        Same URL is used both for GET and POST.
        """
    result_url = '/flow/' + str(step_key) + '/' + str(adapter_id)
    if back_page is not None:
        result_url = result_url + '?back_page=' + str(back_page)
    return result_url
