def modify_via_segment_holder_acts_as_list_method(method, segment)
      segment_holder = segment_holder_for(segment)
      raise segment_not_associated_message(method, segment) unless segment_holder     
      segment_holder.send(method)  
    end
def modify_via_segment_holder_acts_as_list_method(method, segment)
      segment_holder = segment_holder_for(segment)
      raise segment_not_associated_message(method, segment) unless segment_holder     
      segment_holder.send(method)  
    end
This method, together with method missing, is used to allow segments
 to be ordered within a document. It allows an acts_as_list method to be
 passed to the segment_holder holding a segment, so as to alter its position.

 For example:
   document.move_to_top document.segments.last

 will move the last segment so that it becomes the first within
 document.segments.


 The syntax is:

   document.<acts_as_list_method> <the_segment_to_be_moved>

 The segment must already belong to the document