Allows items through whose keys are distinct from the previous item.
source: |-{a:1,b:2}--{a:2,b:3}--{a:2,c:3}--{b:3}--{b:4}-|distinctUntilKeysChanged(): |-{a:1,b:2}-------------{a:2,c:3}--{b:3}--------| Copy
source: |-{a:1,b:2}--{a:2,b:3}--{a:2,c:3}--{b:3}--{b:4}-|distinctUntilKeysChanged(): |-{a:1,b:2}-------------{a:2,c:3}--{b:3}--------|
Allows items through whose keys are distinct from the previous item.