Set<EventHandler> getHandlersForEventType(Class<?> type) {
    return handlersByType.get(type);
  }
Retrieves a mutable set of the currently registered handlers for {@code type}.  If no handlers are currently
registered for {@code type}, this method may either return {@code null} or an empty set.

@param type type of handlers to retrieve.
@return currently registered handlers, or {@code null}.
otto/src/main/java/com/squareup/otto/Bus.java