heron-simple-wordcount-topology broken with docker version 0.20.5-incubating

[jmtd]

Describe the bug

The very first example topology is broken with the latest version of the docker container (which, interestingly, is a micro version ahead of GitHub): 0.20.5-incubating

(the example used in https://github.com/apache/incubator-heron/blob/master/website2/docs/getting-started-docker.md)

To Reproduce
Steps to reproduce the behavior:

1. docker run -it --rm -d -p 8889:8889 -p 8888:8888 --name local-heron apache/heron:0.20.5-incubating supervisord --nodaemon (note version: 0.20.5-incubating)
2. docker exec -it local-heron bash -c "heron submit sandbox /heron/examples/heron-eco-examples.jar org.apache.heron.eco.Eco --eco-config-file /heron/examples/heron_wordcount.yaml"
3. See error

Expected behavior

…
[2022-07-07 14:33:02 +0000] [INFO]: Successfully launched topology 'heron-simple-wordcount-topology' 

Actual behavior

;docker exec -it    local-heron    bash -c "heron submit sandbox  /heron/examples/heron-eco-examples.jar org.apache.heron.eco.Eco --eco-config-file /heron/examples/heron_wordcount.yaml"
[2022-07-07 14:38:15 +0000] [INFO]: Using cluster definition in /usr/local/heron/conf/sandbox
Exception in thread "main" Cannot create property=spouts for JavaBean=org.apache.heron.eco.definition.EcoTopologyDefinition@45b9a632
 in 'string', line 22, column 1:
    name: "heron-simple-wordcount-to ... 
    ^
Can not set java.util.Map field org.apache.heron.eco.definition.EcoTopologyDefinition.spouts to java.util.ArrayList
 in 'string', line 49, column 3:
      - id: "spout-1"
      ^

	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:291)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:172)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:332)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:230)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:220)
	at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:174)
	at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:158)
	at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:491)
	at org.yaml.snakeyaml.Yaml.load(Yaml.java:416)
	at org.apache.heron.eco.parser.EcoParser.loadTopologyFromYaml(EcoParser.java:87)
	at org.apache.heron.eco.parser.EcoParser.parseFromInputStream(EcoParser.java:50)
	at org.apache.heron.eco.Eco.submit(Eco.java:75)
	at org.apache.heron.eco.Eco.main(Eco.java:163)
Caused by: java.lang.IllegalArgumentException: Can not set java.util.Map field org.apache.heron.eco.definition.EcoTopologyDefinition.spouts to java.util.ArrayList
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
	at java.base/jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
	at java.base/jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81)
	at java.base/java.lang.reflect.Field.set(Field.java:780)
	at org.yaml.snakeyaml.introspector.PropertySubstitute.set(PropertySubstitute.java:105)
	at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:286)
	... 12 more
2022-07-07 14:38:15.450 INFO - o.a.heron.eco.parser.EcoParser -                 main - Parsing eco config file
2022-07-07 14:38:15.453 INFO - o.a.heron.eco.parser.EcoParser -                 main - Not performing property substitution.
2022-07-07 14:38:15.453 INFO - o.a.heron.eco.parser.EcoParser -                 main - Not performing environment variable substitution.
2022-07-07 14:38:15.450 INFO - o.a.heron.eco.parser.EcoParser -                 main - Parsing eco config file
2022-07-07 14:38:15.453 INFO - o.a.heron.eco.parser.EcoParser -                 main - Not performing property substitution.
2022-07-07 14:38:15.453 INFO - o.a.heron.eco.parser.EcoParser -                 main - Not performing environment variable substitution.
[2022-07-07 14:38:15 +0000] [ERROR]: Failed to create topology definition file when executing class 'org.apache.heron.eco.Eco' of file '/heron/examples/heron-eco-examples.jar'

Operating System

• OS: Docker version 20.10.5+dfsg1, build 55c4c88 on Debian 11.3
• Version 0.20.5-incubating

Additional context

Version 0.20.4-incubating works!

The file /heron/examples/heron_wordcount.yaml is unchanged between the versions.