diff --git a/generic_trainer/configs.py b/generic_trainer/configs.py
index b5a910a..7a128b1 100644
--- a/generic_trainer/configs.py
+++ b/generic_trainer/configs.py
@@ -79,7 +79,26 @@ def string_to_object(self, key, value):
         :return: object.
         """
         # Value is a class handle
-        if isinstance(value, (list, tuple)):
+        if isinstance(value, dict):
+            # Only convert the dict to an OptionContainer object if they are supposed to. Otherwise, leave it as a dict.
+            if 'model_params' in key or key in ['loss_tracker_params', 'parallelization_params']:
+                assert 'config_class' in value.keys(), ('The value of {} is supposed to be an object of a subclass '
+                                                        'of OptionContainer, but I cannot find the '
+                                                        'class name.'.format(key))
+                try:
+                    config = globals()[value['config_class']]()
+                    config.deserizalize_dict(value)
+                    value = config
+                except KeyError as e:
+                    raise ModuleNotFoundError(
+                        "When loading {} from JSON, the following error occurred when attempting to create the "
+                        "OptionContainer object for it:'\n{}\n"
+                        "To create an OptionContainer object, its class name must be in the global namespace. You can "
+                        "import the proper classes in your driver script using from ... import ..., and pass "
+                        "globals() to load_from_json:\n"
+                        "    configs.load_from_json(filename, namespace=globals())\n".format(key, e)
+                    )
+        elif isinstance(value, (list, tuple)):
             value = [self.string_to_object(key, v) for v in value]
         elif isinstance(value, str) and (res := re.match(r"<class '(.+)'>", value)):
             class_import_path = res.groups()[0].split('.')
@@ -105,7 +124,9 @@ def object_to_string(self, key, value):
         :return: str.
         """
         if isinstance(value, OptionContainer):
+            config_class_name = value.__class__.__name__
             value = value.get_serializable_dict()
+            value['config_class'] = config_class_name
         elif isinstance(value, (dict, int, float, bool)):
             value = value
         elif isinstance(value, (tuple, list)):
@@ -123,14 +144,7 @@ def object_to_string(self, key, value):
 
 @dataclasses.dataclass
 class ModelParameters(OptionContainer):
-
-    def string_to_object(self, key, value):
-        value = super().string_to_object(key, value)
-        if 'model_params' in key and isinstance(value, dict):
-            config = ModelParameters()
-            config.deserizalize_dict(value)
-            value = config
-        return value
+    pass
 
 
 # =============================
@@ -201,18 +215,6 @@ class Config(OptionContainer):
     Task type. Can be 'classification', 'regression'. Currently this only affects the logging of the loss tracker.
     """
 
-    def string_to_object(self, key, value):
-        value = super().string_to_object(key, value)
-        if 'model_params' in key and isinstance(value, dict):
-            config = ModelParameters()
-            config.deserizalize_dict(value)
-            value = config
-        elif key == 'parallelization_params' and isinstance(value, dict):
-            config = ParallelizationConfig()
-            config.deserizalize_dict(value)
-            value = config
-        return value
-
 
 @dataclasses.dataclass
 class InferenceConfig(Config):
@@ -355,17 +357,13 @@ def string_to_object(self, key, value):
             try:
                 value = eval(value)
             except Exception as e:
-                print(
+                raise ModuleNotFoundError(
                     "When loading loss_function from JSON, the following error occurred:'\n{}\n"
                     "To create a loss function object, its class name must be in the global namespace. You can "
                     "import the proper classes in your driver script using from ... import ..., and pass "
                     "globals() to load_from_json:\n"
                     "    configs.load_from_json(filename, namespace=globals())\n".format(e)
                 )
-        elif key == 'loss_tracker_params':
-            configs = LossTrackerParameters()
-            configs.deserizalize_dict(value)
-            value = configs
         return value
 
 @dataclasses.dataclass