recursive_predecessors()
public
@return [Array] the vertices of {#graph}
where `self` is a
{
# File lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph/vertex.rb, line 54
def recursive_predecessors
vertices = predecessors
vertices += vertices.map(&:recursive_predecessors).flatten(1)
vertices.uniq!
vertices
end