fn simple_case_transform_iterator(
input_iterator: impl Iterator<Item = CharacterTransformIteration>,
mapping: impl Fn(char) -> CharacterTransformIteration,
) -> impl Iterator<Item = CharacterTransformIteration>fn simple_case_transform_iterator(
input_iterator: impl Iterator<Item = CharacterTransformIteration>,
mapping: impl Fn(char) -> CharacterTransformIteration,
) -> impl Iterator<Item = CharacterTransformIteration>