#29 shows an implementation of how to add a sequence plot into the matplotlib plots. Unfortunately with the new updates to pyopenms_viz although this feature is highly useful for mass spectrometrists, it has yet to make it into the plotting framework.

The task here is to integrate this feature into the matplotlib backend interface.

1. Create an abstract method in _core.py under SpectrumPlot for adding the peptide sequence, integrate this method into the plot function.
2. in the _matplotlib/core.py file add an additional method for plotting the peptide sequence.
3. In SpectrumConfig in _config.py add new options for "display peptide sequence" - you can choose the name
4. Add appropriate tests, to tests/test_chromatogram.py - ensure that if called with a different backend a NotImplementedError is thrown.

This is one of the more involved PR for a GSoC student however it will provide you with a good foundation of the pyopenms_viz codebase which is beneficial for those working on implementing their own web app.