The top-level keys of an object schema, through refinements,
transforms, and optional, nullable, and default wrappers. For a union (z.union or
z.discriminatedUnion), every key that appears in any of its object
options, in the order they first appear, so one fields list covers
them all. Null for any other shape (a string, a list, a union with no
object option).
The top-level keys of an object schema, through refinements, transforms, and optional, nullable, and default wrappers. For a union (
z.unionorz.discriminatedUnion), every key that appears in any of its object options, in the order they first appear, so onefieldslist covers them all. Null for any other shape (a string, a list, a union with no object option).