[HOTFIX] Change the sample based on current code tree

[bzhaoopenstack]

This is a hotfix for pyflink shell mode.

The output sample has several problems:

1. Need to import the necessary py pkg for avoiding NotDefinitaion
   error.
2. Use the current function for avoiding NoSuchFunction error.

What is the purpose of the change

Improving the developer experience who using pyflink-shell.sh

Brief change log

• 1. Need to import the necessary py pkg for avoiding NotDefinitaion
     error.
• 2. Use the current function for avoiding NoSuchFunction error.

Verifying this change

Exec pyflink-shell.sh and run its sample code.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

[flinkbot]

CI report:

• 14881a0 Azure: FAILURE

Bot commands

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[bzhaoopenstack]

@flinkbot run azure