isUpdatingStatus function
Matches a JuiceEmission whose status is an UpdatingStatus.
state and groups are optional; each is a value (compared with ==)
or a Matcher. groups is compared to the emission's groups as widgets
saw them (see JuiceEmission.groups).
Implementation
m.Matcher isUpdatingStatus({Object? state, Object? groups}) =>
_EmissionMatcher<UpdatingStatus>('UpdatingStatus', state, groups, null);