to answer your previous question:

by_status = map_reduce(lambda r: [(r.requisition_status,)], data=requisitions, include_docs=True)

first arg is the map function, which returns an iterable of key-value pairs. in this case a list of 1 key-value pair. the value is not provided, and due to the include_docs=True param, the doc ('r') is auto-substituted as the value