Add event expectations

[billytrend-cohere]

The changes in this PR update the test_chat_stream and test_stream_equals_true functions in the test_async_client.py and test_client.py files.

Summary

• The test_chat_stream function now collects chat_event.event_type in a set called events during the loop iteration.
• Additional assertions have been added to test_chat_stream to ensure that specific event types ("text-generation", "stream-start", and "stream-end") are present in the events set.
• The test_stream_equals_true function now includes a ValueError assertion for the co.chat call.

Details

• test_async_client.py:
  • The test_chat_stream function now collects chat_event.event_type in a set called events during the asynchronous loop iteration.
  • Additional assertions have been added to test_chat_stream to ensure that the "text-generation", "stream-start", and "stream-end" event types are present in the events set.
• test_client.py:
  • The test_chat_stream function now collects chat_event.event_type in a set called events during the loop iteration.
  • Additional assertions have been added to test_chat_stream to ensure that the "text-generation", "stream-start", and "stream-end" event types are present in the events set.
  • The test_stream_equals_true function now includes a ValueError assertion for the co.chat call.