def render_tag(name, attributes = {}, &block)
      if name =~ /^(.+?):(.+)$/
        render_tag($1) { render_tag($2, attributes, &block) }
      else
        tag_definition_block = @definitions[qualified_tag_name(name.to_s)]
        if tag_definition_block
          stack(name, attributes, block) do |tag|
            tag_definition_block.call(tag).to_s
          end
        else
          tag_missing(name, attributes, &block)
        end
      end
    end
def render_tag(name, attributes = {}, &block)
      if name =~ /^(.+?):(.+)$/
        render_tag($1) { render_tag($2, attributes, &block) }
      else
        tag_definition_block = @definitions[qualified_tag_name(name.to_s)]
        if tag_definition_block
          stack(name, attributes, block) do |tag|
            tag_definition_block.call(tag).to_s
          end
        else
          tag_missing(name, attributes, &block)
        end
      end
    end
Returns the value of a rendered tag. Used internally by Parser#parse.