xFormers attention op arg (#2049)
* allow passing op to xFormers attention
original code by @patil-suraj
huggingface/diffusers@ae0cc0b71f28c0f2c5c27026b18f1bea98b505f1
* correct style by `make style`
* add attention_op arg documents
* add usage example to docstring
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
* add usage example to docstring
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
* code style correction by `make style`
* Update docstring code to a valid python example
Co-authored-by: Suraj Patil <surajp815@gmail.com>
* Update docstring code to a valid python example
Co-authored-by: Suraj Patil <surajp815@gmail.com>
* style correction by `make style`
* Update code exmaple to fully functional
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
Co-authored-by: Suraj Patil <surajp815@gmail.com>
