@Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    SystemStreamMetadata other = (SystemStreamMetadata) obj;
    if (partitionMetadata == null) {
      if (other.partitionMetadata != null)
        return false;
    } else if (!partitionMetadata.equals(other.partitionMetadata))
      return false;
    if (streamName == null) {
      if (other.streamName != null)
        return false;
    } else if (!streamName.equals(other.streamName))
      return false;
    return true;
  }
@return A map of SystemStreamPartitionMetadata that includes offset
        information for each partition.
samza-api/src/main/java/org/apache/samza/system/SystemStreamMetadata.java