public HdfsInputDescriptor getInputDescriptor(String streamId) {
    return new HdfsInputDescriptor(streamId, this);
  }
Gets an {@link HdfsInputDescriptor} for the input stream of this system.
<p>
The message in the stream has no key and the value type is determined by reader type.

@param streamId id of the input stream
@return an {@link HdfsInputDescriptor} for the hdfs input stream
samza-hdfs/src/main/java/org/apache/samza/system/hdfs/descriptors/HdfsSystemDescriptor.java