setDefaultFilters('clear') //This removes all default filters
setDefaultFilters({ filtername: true }) //This sets the filter 'filtername'
//as a default filter
setDefaultFilters({ filtername: true, otherfilter: true }) //This sets both
//'filtername' and 'otherfilter' to be default filters
setDefaultFilters({ filtername: false }) //This makes 'filtername' not a
//default filter

Simply put, setDefaultFilters has one parameter. If the parameter is "clear" then defaultFilters (which isn't exposed to the user) is set to {} . If the parameter is an object, then it loops over each property and sets it on defaultFilters.

When a reference is parsed, it is passed through the filters with the same name as the properties on defaultFilters, as long as it is set to true.