public CollectionSchemaUpdate set(String key, IOperation operation) {
    collectionUpdateData.put(key, operation);
    return this;
  }
public CollectionSchemaUpdate set ( String key , IOperation operation ) { collectionUpdateData . put ( key , operation ) ; return this ; }
A method to set a new Operation for a key. It may be of type ADD, RENAME or DELETE.
Only one operation per key can be specified. Attempt to add a second operation for a any key will override the first one.
Attempt to add a ADD operation for a key which already exists will have no effect.
Attempt to add a DELETE operation for akey which does not exist will have no effect.

@param key (a.k.a JSON Field name) for which operation is being added
@param operation  operation to perform
@return  the updated CollectionSchemaUpdate