Improve Type of BaseListener

[Joecha95]

A detailed description including the pr-template is provided in the pr see #906

Checklist

• [x] The code has been run through pretty yarn run pretty
• [ ] The tests pass on CircleCI
• [ ] You have referenced the issue(s) or other PR(s) this fixes/relates-to
• [x] The PR Template has been filled out (see below)
• [x] Had a beer because you are awesome