Convert SQL and params args to DBAPI2.0 compliant format.

def _convert_params(sql, params):
    """Convert SQL and params args to DBAPI2.0 compliant format."""
    args = [sql]
    if params is not None:
        if hasattr(params, 'keys'):  # test if params is a mapping
            args += [params]
        else:
            args += [list(params)]
    return args