def undo where
      raise "not yet used"
      return unless @delete_buffer
      case @delete_buffer[0]
      when Array
        @delete_buffer.each do |r| 
          insert where, r 
        end
      else
        insert where, @delete_buffer
      end
    end
def undo where
      raise "not yet used"
      return unless @delete_buffer
      case @delete_buffer[0]
      when Array
        @delete_buffer.each do |r| 
          insert where, r 
        end
      else
        insert where, @delete_buffer
      end
    end
a quick method to undo deletes onto given row. More like paste