Returns a sequence containing all the keys present in a map
map:keys( $map as map(*)xs:anyAtomicType*The function map:keys takes any map
as its $map argument and returns the keys that are present in the map as
a sequence of atomic values, in implementation-dependent order.
The function is non-deterministic with respect to ordering (see ). This means that two calls with the same argument are not guaranteed to produce the results in the same order.
The expression map:keys(map{1:"yes", 2:"no"}) returns (1,2).
The number of items in the result will be the same as the number of entries in the map, and the result sequence will contain no duplicate values.
