A.37 library(ugraphs): Unweighted Graphs
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Availability::- use_module(library(ugraphs)).(can be autoloaded)
Sourceneighbours(+Vertex, +Graph, -Vertices)
Unify Vertices with the list of neighbours of vertex Vertex in Graph. Example: 
?- neighbours(4,[1-[3,5],2-[4],3-[],
                 4-[1,2,7,5],5-[],6-[],7-[],8-[]], NL).
NL = [1,2,7,5]
ClioPatria (version V3.1.1-21-gb8003bb)