Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.
The genders of the audience. Strongly encouraged to use the standard
values: “male”, “female”, “unisex”.
At most 5 values are allowed. Each value must be a UTF-8 encoded string
with a length limit of 128 characters. Otherwise, an INVALID_ARGUMENT error
is returned.
The age groups of the audience. Strongly encouraged to use the standard
values: “newborn” (up to 3 months old), “infant” (3–12 months old),
“toddler” (1–5 years old), “kids” (5–13 years old), “adult” (typically
teens or older).
At most 5 values are allowed. Each value must be a UTF-8 encoded string
with a length limit of 128 characters. Otherwise, an INVALID_ARGUMENT error
is returned.