Text at an application boundary needs a precise format. A regular expression search can find a valid substring inside an invalid id, so a complete identifier usually needs fullmatch. JSON decoding turns a string into values, but you still decide what a missing field means and whether an empty string is valid.
Time and files carry their own context. An offset-aware timestamp identifies an instant that can be converted to UTC before formatting. Pathlib reads and writes local paths; in this workspace those paths belong to a virtual filesystem. You will create files only inside a temporary directory and clean them up when the operation ends. The checks include midnight crossings, Unicode characters, missing keys, and extra text around otherwise valid identifiers.