<set>
- A 2-element JSON array that represents a database set value. The
+ Either an <atom>, representing a set with exactly one element, or
+ a 2-element JSON array that represents a database set value. The
first element of the array must be the string "set" and the second
element must be an array of zero or more <atom>s giving the values
in the set. All of the <atom>s must have the same type.