fix import error

[gushiqiao]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @gushiqiao, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the robustness and flexibility of the lightx2v project by addressing potential import errors and expanding model configuration options. It introduces conditional imports for specific transformers components and refines the availability check for Flash Attention, preventing runtime failures due to missing dependencies. Furthermore, it extends quantization capabilities for T5 and XLM-RoBERTa models with a new VLLM FP8 scheme and adds a configurable Rotary Positional Embedding type to the generation pipeline, offering more control over model behavior.

Highlights

• Conditional Imports for Qwen2.5 VL: Imports for Qwen2Tokenizer and Qwen2_5_VLForConditionalGeneration are now conditionally handled with try-except ImportError to prevent crashes if transformers components are unavailable.
• Robust Flash Attention Availability Check: The detection of flash_attn_func is made more resilient by nesting try-except blocks, ensuring FLASH_ATTN_3_AVAILABLE is accurately set even if flash_attn is partially installed.
• VLLM FP8 Quantization Support: Added VllmQuantLinearFp8 import and integration for T5 and XLM-RoBERTa models, enabling a new "fp8-vllm" quantization scheme.
• Configurable RoPE Type in Pipeline: Introduced a rope_type parameter in the pipeline's generator configuration, allowing users to specify the type of Rotary Positional Embedding (defaulting to "torch").

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[gemini-code-assist]

Code Review

This pull request aims to fix import errors by making some dependencies optional. However, the current implementation is incomplete and could lead to runtime errors. I've identified two critical issues where modules are set to None or are left undefined after a failed import, but are then used without proper checks, which would cause the application to crash. My review includes suggestions on how to handle these optional dependencies more robustly. The other changes, such as adding support for a new quantization scheme and a new configuration option, appear to be correct and well-implemented.

[gemini-code-assist]

While this change correctly handles the ImportError for optional dependencies, it introduces a potential runtime error. If transformers is not installed or the specified modules are not available, Qwen2Tokenizer and Qwen2_5_VLForConditionalGeneration will be None. However, they are later used without a None check (e.g., Qwen2Tokenizer.from_pretrained on line 78 and Qwen2_5_VLForConditionalGeneration.from_pretrained on line 74), which will raise an AttributeError. The code should either raise a more informative error if these optional dependencies are required for a certain functionality, or handle the None case gracefully where these classes are used.

[gemini-code-assist]

This change attempts to handle the optional dependency flash_attn, but it's incomplete and will lead to a NameError at runtime if flash_attn is not installed. When the inner except ImportError block is executed, flash_attn_func is not defined. However, the code later calls flash_attn_func (e.g., on line 392) if FLASH_ATTN_3_AVAILABLE is False. The suggested change defines a placeholder function that will raise an informative ImportError at runtime if flash_attn is not available, making the issue easier to debug.

Suggested change

	except ImportError:
	from flash_attn import flash_attn_func
	try:
	from flash_attn import flash_attn_func
	FLASH_ATTN_3_AVAILABLE = False
	FLASH_ATTN_3_AVAILABLE = False
	except ImportError:
	FLASH_ATTN_3_AVAILABLE = False
	except ImportError:
	FLASH_ATTN_3_AVAILABLE = False
	try:
	from flash_attn import flash_attn_func
	except ImportError:
	def flash_attn_func(*args, **kwargs):
	raise ImportError("flash-attn is not installed, which is required when flash_attn_interface is not available.")