FilterGRanges is a virtual subclass of
ProxyGRanges that filters the data from some
delegate GenomicRanges. The actual filtering is
implemented by a subclass. The easiest way to define a subclass is to
call the setFilterGRangesClass function, described here.setFilterGRangesClass(prefix, filter, where = topenv(parent.frame()), ...)filter method. Takes a
single argument: the GenomicRanges to filter. The function
should return a logical vector indicating which records should pass
the filter.setProxyGRangesClasssetProxyGRangesClass, which this function wraps.