code: func (l *List) PageUp() {
  	start := l.start - l.size
  	if start < 0 {
  		l.start = 0
  	} else {
  		l.start = start
  	}
  
  	cursor := l.start
  
  	if cursor < l.cursor {
  		l.cursor = cursor
  	}
  }
docs: // PageUp moves the visible list backward by x items. Where x is the size of the
  // visible items on the list. The selected item becomes the first visible item.
  // If the list is already at the bottom, the selected item becomes the last
  // visible item.