def get_var_from_task_decorator(Cls, upstream_task_id='',
    upstream_return_key='', u_task=None):
    """wrapper for functions that require an fixed input, which is here provided
    by a previous task"""
    upstream_return = {upstream_return_key: 'test'}
    return_value = upstream_return[upstream_return_key]
    Cls.srmfile = return_value
    return Cls
