public void deleteStartpoint(SystemStreamPartition ssp) {
    deleteStartpoint(ssp, null);
  }
Deletes the {@link Startpoint} for a {@link SystemStreamPartition}
@param ssp The {@link SystemStreamPartition} to delete the {@link Startpoint} for.
samza-core/src/main/java/org/apache/samza/startpoint/StartpointManager.java