update comment

Author: FitseTLT

lib/types.ts

@@ -484,6 +484,9 @@ type InitOptions = {
     /**
      * Array of collection keys whose backend returned data can be directly merged into
      * snapshot without selectively picking the existing keys in the existing snapshot data.
+     * For e.g. if oldSnapshotData is {report_1: {name 'Fitsum'}} and BE update is {report_1: {name:'Fitsum2', nickName:'Fitse'}}
+     * if it is fullyMergedSnapshotkey the `nickName` prop that didn't exist in the previous data will be merged
+     * otherwise only existing prop will be picked from the BE update and merged (in this case only name).
      */
     fullyMergedSnapshotKeys?: string[];
 };