Add module which gathers all models

This module collects models dict, which maps model name to function loading this model.

src/category_classification/models/models.py

@@ -0,0 +1,72 @@
+import importlib.util
+import os
+import sys
+import warnings
+from pathlib import Path
+
+def import_model_module(file_path: os.PathLike):
+    module_name = str(Path(file_path).relative_to(os.getcwd())).replace(os.path.sep, ".")
+    spec = importlib.util.spec_from_file_location(module_name, file_path)
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[module_name] = module
+    spec.loader.exec_module(module)
+    return module
+
+
+models = {}
+
+file_dir = Path(__file__).parents[0]
+
+for path in file_dir.glob("*"):
+    if path.is_dir():
+        model_file_path = path / "model.py"
+        if not model_file_path.exists():
+            continue
+        module = import_model_module(model_file_path)
+        name_key = "name"
+        get_model_key = "get_model"
+        name = getattr(module, name_key, None)
+        get_model = getattr(module, get_model_key, None)
+
+        def check_attr_exists(attr_name, attr):
+            if attr is None:
+                warnings.warn(
+                    f"Module {model_file_path} should define attribute '{attr_name}'"
+                )
+                return False
+            return True
+
+        def check_attr_type(attr_name, attr, type):
+            if isinstance(attr, type):
+                return True
+            warnings.warn(
+                f"'{attr_name}' should be of type {type}, but it is of type {type(attr)}"
+            )
+            return False
+
+        def check_attr_callable(attr_name, attr):
+            if callable(attr):
+                return True
+            warnings.warn(f"'{attr_name}' should be callable")
+            return False
+
+        if not check_attr_exists(name_key, name):
+            continue
+        if not check_attr_exists(get_model_key, get_model):
+            continue
+        if not check_attr_type(name_key, name, str):
+            continue
+        if not check_attr_callable(get_model_key, get_model):
+            continue
+
+        models[name] = get_model
+
+
+def get_model(name: str):
+    if name not in models:
+        raise KeyError(f"No model with name {name}")
+    return models[name]()
+
+
+def get_all_model_names():
+    return list(models.keys())