[Python Schema] Fix python schema array map with record

[gaoran10]

Motivation

Currently, the schema type Array and Map couldn't work well with Record.

For example.

class NestedObj(Record):
    na2 = Integer()
    nb2 = Boolean()

class ComplexRecord(Record):
    a = Integer()
    b = Integer()
    arrayNested = Array(NestedObj())

nested_obj = NestedObj(na2=22, nb2=True)
r = ComplexRecord(a=1, b=2, arrayNested=[
    nested_obj, nested_obj, nested_obj
])

error log

  File "/Volumes/shit/Workspaces/GitHubFork/pulsar/pulsar-client-cpp/python/pulsar/schema/definition.py", line 74, in __init__
    self.__setattr__(k, kwargs[k])
  File "/Volumes/shit/Workspaces/GitHubFork/pulsar/pulsar-client-cpp/python/pulsar/schema/definition.py", line 117, in __setattr__
    value = field.validate_type(key, value)
  File "/Volumes/shit/Workspaces/GitHubFork/pulsar/pulsar-client-cpp/python/pulsar/schema/definition.py", line 369, in validate_type
    if type(x) != self.array_type.python_type():
AttributeError: 'NestedObj2' object has no attribute 'python_type'

Modifications

Change the method __init__() of the Record, because decoding data will depend on this method, so we need to use dict data to initialize the Record object.

Add a new method python_type() for Record, the schema type Array and Map need to get python_type of the Record.

Verifying this change

Add test to verify schema type Array and Map work with Record.

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

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: (no)

Documentation

For committer

For this PR, do we need to update docs?

• If yes,

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• If no, label this PR with the no-need-doc label and explain why.