EdgeSituation identifies the edges from a situation (node). This function identifies the edges that emanate from a particular situation in an EventTree.
EdgeSituation(situation, start.situation, num.category)
numeric - it identifies the target situation whose emanating edges are our interesting.
vector - it identifies the situation that begins a new level.
vector - it identifies the number of edges that emanate from situations in each level.
list of lists - each list component is a vector that represents the edges that emanate from a vertice.