Issues running on Python 3.9

[beeman]

There are issues running this package with Python 3.9. Versions 3.6, 3.7 and 3.8 work fine. The current suggestion is to revert to one of these versions.

To reproduce, clone the kin-starter-python and change the python version in the Dockerfile, then build an run that Dockerfile.

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 550, in init
    copy.MergeFrom(new_val)
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 1309, in MergeFrom
    raise TypeError(
TypeError: Parameter to MergeFrom() must be instance of same class: expected Transaction got Transaction.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/main.py", line 14, in <module>
    token_accounts_alice = kin.create_account(private_key_alice)
  File "/usr/local/bin/kin.py", line 21, in create_account
    self.client.create_account(private_key)
  File "/usr/local/lib/python3.9/site-packages/agora/client/client.py", line 330, in create_account
    return retry(self._nonce_retry_strategies, _submit_create_solana_account)
  File "/usr/local/lib/python3.9/site-packages/agora/retry/__init__.py", line 28, in retry
    raise e
  File "/usr/local/lib/python3.9/site-packages/agora/retry/__init__.py", line 21, in retry
    return f(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/agora/client/client.py", line 328, in _submit_create_solana_account
    self._internal_client.create_solana_account(private_key, commitment=commitment, subsidizer=subsidizer)
  File "/usr/local/lib/python3.9/site-packages/agora/client/internal.py", line 291, in create_solana_account
    retry(self._retry_strategies, _create)
  File "/usr/local/lib/python3.9/site-packages/agora/retry/__init__.py", line 28, in retry
    raise e
  File "/usr/local/lib/python3.9/site-packages/agora/retry/__init__.py", line 21, in retry
    return f(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/agora/client/internal.py", line 276, in _create
    req = account_pb_v4.CreateAccountRequest(
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 552, in init
    _ReraiseTypeErrorWithFieldName(message_descriptor.name, field_name)
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 477, in _ReraiseTypeErrorWithFieldName
    six.reraise(type(exc), exc, sys.exc_info()[2])
  File "/usr/local/lib/python3.9/site-packages/six.py", line 718, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 550, in init
    copy.MergeFrom(new_val)
  File "/usr/local/lib/python3.9/site-packages/google/protobuf/internal/python_message.py", line 1309, in MergeFrom
    raise TypeError(
TypeError: Parameter to MergeFrom() must be instance of same class: expected Transaction got Transaction. for field CreateAccountRequest.transaction