Optimize TrainProcessService Singleton Pattern Implementation

[kevin-mindverse]

Changes

TrainProcessService Class Changes

1. Parameter Validation Enhanced: Modified the TrainProcessService initialization function to require the current_model_name parameter, ensuring it cannot be None, thus guaranteeing a valid model name at all times
2. Singleton Access Interface: Added the get_instance() class method, providing a unified interface for obtaining the singleton instance, conforming to standard singleton pattern design

Route Layer Adaptation Updates

1. Invocation Method Update: Updated direct TrainProcessService instance construction calls to use the get_instance() method
2. Code Format Optimization: Simplified some instance creation code formats for improved readability
3. Redundant Endpoint Removal: Removed the no-longer-needed "/model_name" GET route

Benefits

1. Code Consistency: Ensured access consistency through a single interface for obtaining the singleton instance
2. Enhanced Parameter Validation: Prevents creation of invalid instances without a model name
3. Clear Structure: Defined clear boundaries for singleton creation and retrieval, better conforming to design pattern standards

Testing Notes

Please test the following scenarios to ensure functionality:

1. Creating a new TrainProcessService instance with a valid model name
2. Obtaining an existing instance using get_instance()
3. Verifying singleton state consistency by calling functions like reset_progress and stop_process

[kevinaimonster]

LGTM