fix: refactor method to properly release vllm instance resources

[e7217]

I have investigated the related issue(#1003), and it seems that the root cause of the problem is the complexity involved in removing the allocated resources.

The issue did not occur when only a single task was performed, as shown below:

...
- node_type: generator
  ...
  modules:
    - module_type: vllm
      llm: meta-llama/Llama-3.2-1B-instruct
      temperature: 0.1
      max_tokens: 128
      max_model_len: 200
      gpu_memory_utilization: 0.3

However, after adding another scenario, the error occurred. It seems that the error arose during the process of reinitializing the vllm model when the following change was made:

temperature: [ 0.1, 1.0 ]

I have addressed this issue in the code, and I would appreciate it if you could review it.

This PR only addresses the changes related to the destructor, and I will add further details regarding the issue on the issue page.

Thank you.

references

• [Misc]: Invariant encountered: value was None when it should not be vllm-project/vllm#10284
• Is there a way to terminate vllm.LLM and release the GPU memory vllm-project/vllm#1908

[vkehfdl1]

Thank you very much!