public Set<SystemStreamPartition> getSspsExcludingSideInputs() {
    return this.sspsExcludingSideInputs;
  }
Returns the {@link SystemStreamPartition}s excluding the side-input SSPs. For the high-level API, watermarks and
end-of-stream messages are propagated based on their input SSPs. However, the Samza framework does not give side
input messages to the high-level operator tasks. Therefore, the operators need to know the input SSPs excluding the
side input SSPs. See SAMZA-2303 for more details.
samza-core/src/main/java/org/apache/samza/context/TaskContextImpl.java