private String getSamzaProperty(SystemStream systemStream, String property) {
    if (!property.startsWith(SAMZA_PROPERTY)) {
      throw new IllegalArgumentException(
        String.format("Attempt to fetch a non samza property for SystemStream %s named %s", systemStream, property));
    }

    String streamVal = getAllStreamProperties(systemStreamToStreamId(systemStream)).get(property);
    return (streamVal != null) ? streamVal : getSystemStreamProperties(systemStream.getSystem(), systemStream.getStream()).get(property);
  }
Gets the specified Samza property for a SystemStream. A Samza property is a property that controls how Samza
interacts with the stream, as opposed to a property of the stream itself.

First, tries to map the systemStream to a streamId. This will only find a streamId if the stream is a physical name
(explicitly mapped physical name or a stream id without a physical name mapping). That means this will not map a
stream id to itself if there is a mapping from the stream id to a physical stream name. This also requires that the
stream id is mapped to a system in the config.
If a stream id is found:
1) Look for "streams.{streamId}.{property}" for the stream id.
2) Otherwise, look for "systems.{systemName}.streams.{streamName}.{property}" in which the systemName is the system
mapped to the stream id and the streamName is the physical stream name for the stream id.
3) Otherwise, look for "systems.{systemName}.default.stream.{property}" in which the systemName is the system
mapped to the stream id.
If a stream id was not found or no property could be found using the above keys:
1) Look for "systems.{systemName}.streams.{streamName}.{property}" in which the systemName is the system in the
input systemStream and the streamName is the stream from the input systemStream.
2) Otherwise, look for "systems.{systemName}.default.stream.{property}" in which the systemName is the system
in the input systemStream.
3) or null

@param systemStream the SystemStream for which the property value will be retrieved.
@param property the samza property key (including the "samza." prefix); for example, for both
                "streams.streamId.samza.prop.key" and "systems.system.streams.streamName.samza.prop.key", this
                argument should have the value "samza.prop.key"
@return the property value
samza-core/src/main/java/org/apache/samza/config/StreamConfig.java