What is the test for interpreting a voter initiative, including one amending the state Constitution?

"In interpreting a voter initiative, including one amending the state Constitution, we apply the same principles governing statutory construction. We first consider the initiative's language, giving the words their ordinary meaning and construing this language in the context of the statute and initiative as a whole. If the language is not ambiguous, we presume the voters intended the meaning apparent from that language, and we may not add to the statute or rewrite it to conform to some assumed intent not apparent from that language. If the language is ambiguous, courts may consider ballot summaries and arguments in determining the voters' intent and understanding of a ballot measure. [Citation.] [Citation.] Our job is to ascertain and declare what is in terms or in substance contained in the provision, not to insert what has been omitted or omit what has been inserted. [Citation.] We adopt a construction that will effectuate the voters' intent, giv[ing] meaning to each word and phrase, and avoid absurd results. [Citations.] [Citation.]" (Santos v. Brown (2015) 238 Cal.App.4th 398, 409, 189 Cal.Rptr.3d 234.)