with_layout_format

# File actionpack/lib/action_view/lookup_context.rb, line 226
    def with_layout_format
      if formats.size == 1
        yield
      else
        old_formats = formats
        _set_detail(:formats, formats[0,1])

        begin
          yield
        ensure
          _set_detail(:formats, old_formats)
        end
      end
    end