InstanceChecker: Implement filter arc attributes
Sadly, filters are not just overlays of each other. There are some extra attributes to be taken into account:
filter.complement: https://www.xbrl.org/specification/variables/rec-2009-06-22/variables-rec-2009-06-22+corrected-errata-2013-11-18.html#term-filter-complement This seems to add facts back based on the filter, rather than subtract it. So, filters cannot just be deduced from each other. When a comlementing filter is found I guess we have to add the 'filtered' facts back into the list of available facts.
filter.cover:https://www.xbrl.org/specification/variables/rec-2009-06-22/variables-rec-2009-06-22+corrected-errata-2013-11-18.html#term-covering-filter Not sure how to intepret this one yet. Seems to be used to decide wether or not facts are covered by a filter (filtered by a filter?) Although if this is the case, what is the point of the filter to begin with?