README.rst listening code bug due to message schema

[Quemoy]

Hello. In README.rst, a suggested sample code for listening to message is:

def callback(message, subscription_id):
    print('Subscription ID: {}: Message: {}'.format(subscription_id, message.data.__str__()))
    return True  # If desired return False to stop the message flow. This will unblock the process as well.

listener.listen(callback, maximum_messages=10)  # Omitting maximum_messages means you will continue to get messages as they appear. Can be a firehose. Use with caution.
# You may pass subscription ID as a parameter to the listen function

However, using this code produces the following error:

Input In [1], in callback(message, subscription_id)
      8 def callback(message, subscription_id):
      9     print('Subscription ID: {}: Message: {}'.format(subscription_id, 
---> 10                                                     message.data.__str__()))
     11     return True

AttributeError: 'dict' object has no attribute 'data'

This seems like because the schema for a message is different. This is what a message looks like from the streams:

{'an': 'DUBQTELH20230317ej3g00046', 'document_type': 'article', 'action': 'del', 's
ource_code': 'DUBQTELH', 'source_name': 'Telegraph Herald', 'publication_date': '2023-03-16T00:00:00
.000Z', 'publication_datetime': '2023-03-16T00:00:00.000Z', 'modification_date': '2023-03-20T04:33:5
9.600Z', 'modification_datetime': '2023-03-20T04:33:43.000Z', 'ingestion_datetime': '2023-03-20T04:3
3:43.000Z', 'attrib_code': 'DUBQTELH', 'authors': [], 'clusters': []}

e.g., there's no longer a data field in the message.

The code in the demo directory does not seem to have this problem. However, the documentation on the developer platform does say that a message has a 'data' field.

[cninowize]

Thank you for bringing this up! The issue you're encountering happens because the message object is already a dictionary, and the data field does not exist at the top level — the relevant information is one level below data.

In your callback function, instead of trying to access message.data, you can directly access the dictionary fields or handle the message object appropriately. Here's the corrected snippet:

def callback(message, subscription_id):
    print('Subscription ID: {}: Message: {}'.format(subscription_id, message))
    return True  # If desired, return False to stop the message flow. This will unblock the process as well.

listener.listen(callback, maximum_messages=10)  # Omitting maximum_messages means you will continue to get messages as they appear.

This will work as message is already a dictionary representing the message payload. There's no need to further access a data attribute.

Additionally, we'll consider clarifying this in the README and documentation to prevent confusion for others in the future. Thanks again for flagging this!