question: protected List < Operation > addPreOperations ( final Operation < ? , ? > previousOp , final Operation < ? , ? > currentOp ) { if ( doesOperationNeedValidating ( previousOp , currentOp ) ) { return Collections . singletonList ( ( Operation ) createValidateOperation ( ( Validatable < ? > ) currentOp ) ) ; } return Collections . emptyList ( ) ; }
target:  Adds validation operations for any validatable operations.