code: func (f *Flex) RemoveItem(p Primitive) *Flex {
  	for index := len(f.items) - 1; index >= 0; index-- {
  		if f.items[index].Item == p {
  			f.items = append(f.items[:index], f.items[index+1:]...)
  		}
  	}
  	return f
  }
docs: // RemoveItem removes all items for the given primitive from the container,
  // keeping the order of the remaining items intact.