public Builder key(final QueryKey value) {
            this.key = value;
            return this;
        }
@param value A unique key to identify the instance of the search by. This key is used to identify multiple
             requests for the same search when running in incremental mode.
@return The {@link Builder}, enabling method chaining
stroom-query/stroom-query-api/src/main/java/stroom/query/api/SearchRequest.java