code: def nodes_by_eigenvalue(self, treshold=0.0):
          
          nodes = [(n.eigenvalue, n) for n in self.nodes if n.eigenvalue > treshold]
          nodes.sort(); nodes.reverse()
          return [n for w, n in nodes]
docs: Returns nodes sorted by eigenvector centrality.
          Nodes with a lot of incoming traffic will be at the front of the list