def id(id)
      return (id.is_a? Fixnum or id.is_a? Integer) ? id : @column_keys.index(id)
    end
def id(id)
      return (id.is_a? Fixnum or id.is_a? Integer) ? id : @column_keys.index(id)
    end
def renderer(id)
      each_renderer do |r|
        return r if r.model_col == id(id)
      end
      return nil
    end
  Returns the number of the given column ID.  This is very useful when you're
  working with Gtk's methods because they require column numbers (not Column IDs)
  This method converts the column ID symbols from the VR::ListView#new constructor
  to Integers:

   @view = VR::ListView.new(:name => String, :date => VR::Col::CalendarCol)

   Later in code...

   iter = get_iter(path)
   col_num = id(:date)  # 1
   iter[col_num]

  You won't need to use this when adding rows with VR::ListView#add_row, and
  you also have the option of converting the whole iter to use column IDs (symbols)
  using VR::ViewCommon#vr_row.