from modelverse_kernel.primitives import PrimitiveFinished

def reverseKeyLookup(a, b, **remainder):
    edges = yield [("RO", [a])]
    expanded_edges = yield [("RE", [i]) for i in edges]
    for i, edge in enumerate(expanded_edges):
        if b == edge[1]:
            # Found our edge: edges[i]
            outgoing = yield [("RO", [edges[i]])]
            result = yield [("RE", [outgoing[0]])]
            raise PrimitiveFinished(result[1])

    result = yield [("CNV", ["(unknown: %s)" % b])]
    raise PrimitiveFinished(result)