Right now, preprocessing functions take an output_file parameter indicating whether output should be saved, and a separate preprocessing_path parameter indicating which folder it should be saved to. This should be changed such that preprocessing_path=None indicates that no output file should be generated. (i.e. the output_file parameter isn't necessary.)
Right now, band-pass filtering is done on all channels, including PupilSize, GazeX, and GazeY which should not be filtered. Similarly, these channels can be marked as bads, but they should never be bads.