Communications between a party's attorney and a testifying expert witness in an action subject to this chapter are protected from discovery regardless of the form of the communications, except to the extent that the communications:
(1) relate to compensation for the expert's study or testimony;
(2) identify facts or data that the party's attorney provided and that the expert considered in forming the opinions the expert will express; or
(3) identify assumptions that the party's attorney provided and that the expert relied on in forming the opinions the expert will express.