key
Identifies which metric this filter applies to.
Matches ReportMetric.key. How you use this key to apply or re-apply a filter depends on the
filter type: for RangeReportFilter pass it in Query.report's rangeFilters argument; for
WildcardReportFilter pass it in the wildcardFilters argument; for OptionsReportFilter
traverse ReportFilterOption.report on the chosen option instead — there is no
optionsFilters argument on Query.report.
Arguments
key doesn't take any arguments.
Type
This field resolves to String!.