Consider type hints and a checker

A number of times we inject code and exceptions to check typing - e.g. during read we check IO objects are paired with appropriate artifacts. These checks could be replaced with type hints and a pass by mypy.

The issue names no files or tests; start by locating the read path and its IO-object and artifact compatibility checks. Compare those checks with the existing type annotations, then determine the mypy configuration and verify that the relevant code passes without injected typing checks.

Written by the indexing model from the issue text.