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* Interface with constants for the different layouts.
* @package ampproject/amp-toolbox
const NODISPLAY = 'nodisplay';
const RESPONSIVE = 'responsive';
const FIXED_HEIGHT = 'fixed-height';
const CONTAINER = 'container';
const FLEX_ITEM = 'flex-item';
const INTRINSIC = 'intrinsic';
const SIZE_DEFINED_LAYOUTS = [