Update to flash-attn2

[Ding3LI]

Update Comments

Modified scgpt/model/model.py & scgpt/model/multiomic_model.py for flash-attn2. Updated README.md with flash-attn2 installation and notes.

Updated Dependencies

flash-attn 1.x --> flash-att 2.x

Is Code Tested?

Yes. The updated code was tested on A100 GPU (Linux), and it works fine doing fine-tuning integration with the latest Flash Attention 2.

Note:
In the current version of code, scGPT uses FlashMHA. And the updated flash-attn2 uses a module named mpa.py. The details of newer MHA implementation can be found HERE starting at line 354 flash_attn/modules/mha.py

[NozomiMizore]

In ur latest changes, u have set the use_flash_attn=False in model.py. I have also modified the code to it. It seems like the model actually didn't call the flash-attn but call the standard mha. And the metric result of my "tutorial_annotation" is terrible. But if I don't set use_flash_attn to False as you did, the program would get some error about padding_mask. Do u have the same problem?