Returns an array of encodings, accepted by the requestor, in order of preference. If there are no encodings supplied by the requestor, undefined is returned.

For a given set of encodings, return the best match accepted by the requestor. If there are no encodings that match, then the method returns undefined.

NOTE: You should always supply identity as one of the encodings to ensure that there is a match when the Accept-Encoding header is part of the request.