def parse_project_id(project_id):
    """Simple check for project id.

    :param project_id: a numeric project id, int or string.
    :return: a unified project id.
    :rtype: :class:`str`
    """
    try:
        int(project_id)
    except ValueError:
        raise ValueError("Project id should be convertible to integer")
    return str(project_id)