def put_event_stream(ApplicationId=None, WriteEventStream=None):
    """
    Use to create or update the event stream for an app.
    
    
    :example: response = client.put_event_stream(
        ApplicationId='string',
        WriteEventStream={
            'DestinationStreamArn': 'string',
            'ExternalId': 'string',
            'RoleArn': 'string'
        }
    )
    
    
    :type ApplicationId: string
    :param ApplicationId: [REQUIRED] ApplicationId

    :type WriteEventStream: dict
    :param WriteEventStream: [REQUIRED] EventStream to write.
            DestinationStreamArn (string) -- The Amazon Resource Name (ARN) of the Amazon Kinesis stream or Firehose delivery stream to which you want to publish events. Firehose ARN: arn:aws:firehose:REGION:ACCOUNT_ID:deliverystream/STREAM_NAME Kinesis ARN: arn:aws:kinesis:REGION:ACCOUNT_ID:stream/STREAM_NAME
            ExternalId (string) -- The external ID assigned the IAM role that authorizes Amazon Pinpoint to publish to the stream.
            RoleArn (string) -- The IAM role that authorizes Amazon Pinpoint to publish events to the stream in your account.
            

    :rtype: dict
    :return: {
        'EventStream': {
            'ApplicationId': 'string',
            'DestinationStreamArn': 'string',
            'ExternalId': 'string',
            'LastModifiedDate': 'string',
            'LastUpdatedBy': 'string',
            'RoleArn': 'string'
        }
    }
    
    
    :returns: 
    (dict) -- PutEventStream Response
    EventStream (dict) -- Model for an event publishing subscription export.
    ApplicationId (string) -- The ID of the application from which events should be published.
    DestinationStreamArn (string) -- The Amazon Resource Name (ARN) of the Amazon Kinesis stream or Firehose delivery stream to which you want to publish events. Firehose ARN: arn:aws:firehose:REGION:ACCOUNT_ID:deliverystream/STREAM_NAME Kinesis ARN: arn:aws:kinesis:REGION:ACCOUNT_ID:stream/STREAM_NAME
    ExternalId (string) -- The external ID assigned the IAM role that authorizes Amazon Pinpoint to publish to the stream.
    LastModifiedDate (string) -- The date the event stream was last updated in ISO 8601 format.
    LastUpdatedBy (string) -- The IAM user who last modified the event stream.
    RoleArn (string) -- The IAM role that authorizes Amazon Pinpoint to publish events to the stream in your account.
    
    
    
    
    
    """
    pass
