In Sav-On Drugs, Inc. v. Superior Court (1975) 15 Cal.3d 1, after discussing the privilege created by section (Rev. & Tax. Code, 7056), the court acknowledged that there may be circumstances under which discovery of tax returns would be permissible, when it stated (at p. 8): "It may be noted in conclusion that no attempt has been made herein to define the full ambit of the privilege considered above, nor are we called upon to determine whether under other circumstances discovery of tax returns and records would be permissible."