@param queryDict A dictionary with all the necessary conditions for retrieving objects.
@discussion If a complex query needs to be performed and if it is difficult to specify it using the query methods, a dictionary can be provided that specifies all the conditions. The dictionary should be as per the JSON format specified in the REST API docs.
@abstract Advises the operation object that it should stop executing its task.
//Obj-C
[blogQuery cancelRequests];
//Swift
blogQuery.cancelRequests()
@discussion This method does not force your operation code to stop. Instead, it updates the object’s internal flags to reflect the change in state. If the operation has already finished executing, this method has no effect. Canceling an operation that is currently in an operation queue, but not yet executing, makes it possible to remove the operation from the queue sooner than usual.