getAutoAnimatableElements( fromSlide, toSlide ) {

		let matcher = typeof this.Reveal.getConfig().autoAnimateMatcher === 'function' ? this.Reveal.getConfig().autoAnimateMatcher : this.getAutoAnimatePairs;

		let pairs = matcher.call( this, fromSlide, toSlide );

		let reserved = [];

		// Remove duplicate pairs
		return pairs.filter( ( pair, index ) => {
			if( reserved.indexOf( pair.to ) === -1 ) {
				reserved.push( pair.to );
				return true;
			}
		} );

	}
Get a list of all element pairs that we can animate
between the given slides.

@param {HTMLElement} fromSlide
@param {HTMLElement} toSlide

@return {Array} Each value is an array where [0] is
the element we're animating from and [1] is the
element we're animating to