You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ignorefields.m
    path of file: ./repos/fieldtrip/utilities/private
    
    the code of the file until where you have to start completion: function ignore = ignorefields(purpose)

    
function ignore = ignorefields(purpose)

% IGNOREFIELDS returns a list of fields that can be present in the cfg structure that
% should be ignored at various places in the code, e.g. for provenance, history,
% size-checking, etc.

switch purpose

  case 'append