def template(keys = :term)
      tmpl = columns.map do |column|
        next unless attribute = attribute_for(column)
        [attribute.send(keys), entity.send(keys)]
      end.compact
      return tmpl.compact unless entity.is_core
      entity.extensions.each do |xtn|
        tmpl << xtn.model_get.template(keys)
      end
      tmpl
    end
def template(keys = :term)
      tmpl = columns.map do |column|
        next unless attribute = attribute_for(column)
        [attribute.send(keys), entity.send(keys)]
      end.compact
      return tmpl.compact unless entity.is_core
      entity.extensions.each do |xtn|
        tmpl << xtn.model_get.template(keys)
      end
      tmpl
    end
Returns a nested array of all terms in the order values
 will be returned by #to_a. Each item in the nested array will be an array
 with the entity term at index 0 and the attribute term at index 1.