public SubClass withPriority(int priority) {
    this.priorityOptional = Optional.of(priority);
    return (SubClass) this;
  }
If one or more streams have a priority set (any positive integer), they will be processed with higher priority
than the other streams.
<p>
You can set several streams to the same priority, or define multiple priority levels by assigning a
higher number to the higher-priority streams.
<p>
If a higher-priority stream has any messages available, they will always be processed first;
messages from lower-priority streams are only processed when there are no new messages on higher-priority inputs.

@param priority priority for this input stream
@return this input descriptor
samza-api/src/main/java/org/apache/samza/system/descriptors/InputDescriptor.java