def get_open_pull_requests(repo=None, base=None):

    """
    retrieve open pull requests from specified repository
    :param repo:
    :param base:
    :return github.PaginatedList.PaginatedList
    """

    if not repo:
        raise ValueError("you must provide repo")

    if not base:
        raise ValueError("you must provide base branch")

    return repo.get_pulls(state='open', sort='created', base=base)