topological sort graph

[TC]

Does neo4j has topological sort function for directed graph data(with loops)?

If I follow

 for ( Path position : db.traversalDescription()

                .depthFirst()

                .relationships( Rels.LIKES, Direction.INCOMING )

                .traverse( node ) )

but how to choose the starting node in topo sort order for this graph?

[Michael Hunger]

You mean in general? I think toposort is only defined for trees? You can ignore the loops though in a traversal description (Uniqueness.Relationship-Global) and in theory start at any random node in the graph to find the topologically first (tree-root). 

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[TC]

The graph maybe has loop inside and multiple source node(no incoming edges).

Even using traversal description (Uniqueness.Relationship-Global), it will need a starting node from users to begin. So it cannot deal with multiple source node graph. 

like figure in this wiki page:http://en.wikipedia.org/wiki/Topological_sorting

[TC]

i follow the algo in the wiki page below: So during while loop, i remove a node n from s and traversal each path(depth 1). and remove this path from graph. I can set property to this relationship like visited. but how to check no other incoming edges into node m. Does this mean i have make traversal from m inside the traversal from n? 

L ← Empty list that will contain the sorted elements
S ← Set of all nodes with no incoming edges
while S is non-empty do
    remove a node n from S
    add n to tail of L
    for each node m with an edge e from n to m do
        remove edge e from the graph
        if m has no other incoming edges then
            insert m into S
if graph has edges then
    return error (graph has at least one cycle)
else 
    return L (a topologically sorted order)