code: func (g *Graph) Int64(def ...int64) int64 {
  	n, ok := _int64f(g.String())
  	if !ok {
  		if len(def) == 0 {
  			return 0
  		}
  		return def[0]
  	}
  	return n
  }
docs: // Int64 returns the node as an int64. If the node is not a number, it
  // returns 0, or the default value if given.