code: def hops(node1, node2):
      
      if node1 == node2:
          return 0
      elif set(node1.interfaces) & set(node2.interfaces):
          # they share a common interface
          return 1
      else:
          # Not implemented yet, graphsearch to find min hops between two nodes
          return 0
docs: returns # of hops it takes to get from node1 to node2, 1 means they're on the same link