Code review comment for lp:~zorba-coders/zorba/bug-1189804

Looks good! Here are some comments:

- Did you check that the invalid option type error does not exist already? Will it be consistent also in all other modules?
- Should JSONiq modules not be suffixed as .jq (but it's only cosmetics of course).
- empty-sequence() -> ()
- array() -> array
- Why remove variadic="true"? I forgot what the semantics for this attribute are.
- In the implementation of map:key: why not reserve the vector size at the beginning (unless you cannot get the size of an ItemVector in constant time?).