A petition under section 30-3415 or 30-3421 may be filed by any of the following: (1) The principal; (2) The attorney in fact; (3) The spouse, parent, sibling, or adult child of the principal; (4) A close adult friend of the principal; (5) The guardian of the principal; (6) The attending physician or other health care provider; or (7) Any other interested party.