generalize helper for loading module from source (#2862)

api/core/utils/module_import_helper.py

@@ -0,0 +1,62 @@
+import importlib.util
+import logging
+import sys
+from types import ModuleType
+from typing import AnyStr
+
+
+def import_module_from_source(
+        module_name: str,
+        py_file_path: AnyStr,
+        use_lazy_loader: bool = False
+) -> ModuleType:
+    """
+    Importing a module from the source file directly
+    """
+    try:
+        existed_spec = importlib.util.find_spec(module_name)
+        if existed_spec:
+            spec = existed_spec
+        else:
+            # Refer to: https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
+            spec = importlib.util.spec_from_file_location(module_name, py_file_path)
+            if use_lazy_loader:
+                # Refer to: https://docs.python.org/3/library/importlib.html#implementing-lazy-imports
+                spec.loader = importlib.util.LazyLoader(spec.loader)
+        module = importlib.util.module_from_spec(spec)
+        if not existed_spec:
+            sys.modules[module_name] = module
+        spec.loader.exec_module(module)
+        return module
+    except Exception as e:
+        logging.exception(f'Failed to load module {module_name} from {py_file_path}: {str(e)}')
+        raise e
+
+
+def get_subclasses_from_module(mod: ModuleType, parent_type: type) -> list[type]:
+    """
+    Get all the subclasses of the parent type from the module
+    """
+    classes = [x for _, x in vars(mod).items()
+               if isinstance(x, type) and x != parent_type and issubclass(x, parent_type)]
+    return classes
+
+
+def load_single_subclass_from_source(
+        module_name: str,
+        script_path: AnyStr,
+        parent_type: type,
+        use_lazy_loader: bool = False,
+) -> type:
+    """
+    Load a single subclass from the source
+    """
+    module = import_module_from_source(module_name, script_path, use_lazy_loader)
+    subclasses = get_subclasses_from_module(module, parent_type)
+    match len(subclasses):
+        case 1:
+            return subclasses[0]
+        case 0:
+            raise Exception(f'Missing subclass of {parent_type.__name__} in {script_path}')
+        case _:
+            raise Exception(f'Multiple subclasses of {parent_type.__name__} in {script_path}')