Improve the implementation of Mapper

We should probably avoid using the magent patter. @travisbrown had some thoughts on how to improve it.

Start by locating the Mapper implementation and reviewing the discussion or guidance from @travisbrown about the magnet pattern. The issue does not name files, tests, or a defined completion criterion, so the desired replacement and validation steps need to be established before work begins.

Written by the indexing model from the issue text.