default OUT visit(IN input, StartpointSpecific startpointSpecific) {
    throw new UnsupportedOperationException("StartpointSpecific is not supported.");
  }
Performs a sequence of operations using IN and {@link StartpointSpecific} and returns the result of the execution.
@param input the input metadata about the startpoint.
@param startpointSpecific the {@link Startpoint} that represents the specific offset.
@return the result of executing the operations defined by the visit method.
samza-api/src/main/java/org/apache/samza/startpoint/StartpointVisitor.java