Move foldlWithKeyWith, foldrWithKeyWith, foldlWithKey, foldlWithKey', foldrWithKey, and foldrWithKey' to Internal module.
Change Foldable imports for Internal module.
Rewrite foldl' and foldr' in terms of foldlWithKey' and foldrWithKey' respectively.
Define foldl and foldr for Foldable instance of Node.
Rewrite foldl and foldr in terms of Foldable instance.
Rewrite elems in terms of foldr.
Implemented `mapMaybe`
Implemented `mapEither`
Remove redundant brackets.
Substitute lambdas with equivalent 'const'.
Resolve minKey shadowing warning.
Implemented query functions
Implemented `insert` and `delete`
Implemented combine functions
Documentation for `splitLookup` fixed
Implemented `map`
Implemented fold functions
Implemented min/max functions
Implemented elems
Implemented ordered list functions