code: func (net *Network) SetFallbackNodes(nodes []*Node) error {
  	nursery := make([]*Node, 0, len(nodes))
  	for _, n := range nodes {
  		if err := n.validateComplete(); err != nil {
  			return fmt.Errorf("bad bootstrap/fallback node %q (%v)", n, err)
  		}
  		// Recompute cpy.sha because the node might not have been
  		// created by NewNode or ParseNode.
  		cpy := *n
  		cpy.sha = crypto.Keccak256Hash(n.ID[:])
  		nursery = append(nursery, &cpy)
  	}
  	net.reqRefresh(nursery)
  	return nil
  }
docs: // SetFallbackNodes sets the initial points of contact. These nodes
  // are used to connect to the network if the table is empty and there
  // are no known nodes in the database.