value: 3 Encoded as number, or the strings "NaN", "Infinity", or
"-Infinity".
TIMESTAMP
value: 4 Must be between 0AD and 9999AD. Encoded as string according to
time_format, or, if
that format is not set, then in RFC 3339 date-time format, where
time-offset = "Z" (e.g. 1985-04-12T23:20:50.52Z).
STRING
value: 6 Encoded as string.
ARRAY
value: 8 Encoded as list, where the list elements are represented according to
value: 9 Encoded as struct, where field values are represented according to
struct_type.
CATEGORY
value: 10 Values of this type are not further understood by AutoML,
e.g. AutoML is unable to tell the order of values (as it could with
FLOAT64), or is unable to say if one value contains another (as it
could with STRING).
Encoded as string (bytes should be base64-encoded, as described in RFC
4648, section 4).
