Refactor helpers for better readability

**Feature request**
It would be great to have filtering for parsers.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_filtering` with default `false`.

Start by locating the parser configuration and the code paths that handle parser input. Determine how an `enable_filtering` option with a default of `false` should affect parser behavior, then confirm the expected filtering behavior and add coverage before considering the work done.

Written by the indexing model from the issue text.