@interface SCPCancelable : NSObject
An object representing an action that can be canceled.
Indicates whether the command has completed. After the command has completed, subsequent calls to cancel will fail.
@property (nonatomic, readonly) BOOL completed;
Attempts to cancel the action in progress. If the action could not be canceled, e.g. it has already completed, the completion block will be called with an error. Otherwise, the completion block will be called with nil.
- (void)cancel:(nonnull SCPErrorCompletionBlock)completion;