See: Description
| Interface | Description | 
|---|---|
| Bundle<T,CollectionT> | An immutable collection of elements which are part of a  PCollection. | 
| ExecutionDriver | Drives the execution of a  Pipelineby scheduling work. | 
| PipelineMessageReceiver | Handles failures in the form of exceptions. | 
| Class | Description | 
|---|---|
| StructuralKey<K> | A (Key, Coder) pair that uses the structural value of the key (as provided by  Coder.structuralValue(Object)) to perform equality and hashing. | 
| Enum | Description | 
|---|---|
| ExecutionDriver.DriverState | The state of the driver. |