Correct bad variable being passed to callback, it should have been null.
Removed storing response in each operation.
Added dispatchAsync method to operations.
Added docblock for createrequest.
Added isErrorResponse and shouldResponseBeProcessed to both generated operations and the generated API class. This allows for per-API and per-operation decisions about what constitutes an error response, and whether a response contains valid data - e.g. HTTP 201 and 202 response may not contain valid data.
Added more comments.