@Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    Startpoint that = (Startpoint) o;
    return Objects.equal(creationTimestamp, that.creationTimestamp);
  }
Applies the {@link StartpointVisitor}'s visit methods to the {@link Startpoint}
and returns the result of that operation.
@param input the metadata associated with the startpoint.
@param startpointVisitor the visitor of the startpoint.
@return the result of applying the visitor on startpoint.
samza-api/src/main/java/org/apache/samza/startpoint/Startpoint.java