_getAlignStyle(align, x, y) {
    return {
      ...this._getXCSS(align.horizontal, x),
      ...this._getYCSS(align.vertical, y)
    };
  }
Get a CSS mixin for a proper positioning of the element.
@param {Object} align object with horizontal and vertical prop strings.
@param {number} x X position.
@param {number} y Y position.
@returns {Object} Object, that may contain `left` or `right, `top` or
`bottom` properties.
@private