where method
Adds field filters to the subscription.
See all(..), either(..), eq(..), le(..), ge(..), lt(..), gt(..).
If called multiple times, the composite filters are composed with the ALL operator, i.e.
an entity state should pass all of the composite filters to match the subscription.
Implementation
StateSubscriptionRequest<M> where(FilterOrComposite filter) {
_filters.add(filter._toProto());
return this;
}