diff --git a/gltflib/models/attributes.py b/gltflib/models/attributes.py
index 56b4ccd..95ff9df 100644
--- a/gltflib/models/attributes.py
+++ b/gltflib/models/attributes.py
@@ -1,20 +1,36 @@
-from dataclasses import dataclass
-from dataclasses_json import dataclass_json
-from typing import Optional
+import copy
+import json
 
-
-@dataclass_json
-@dataclass
+# Attributes is a special case, it can have custom attrs
 class Attributes:
-    """
-    Helper type for describing the attributes of a primitive. Each property corresponds to mesh attribute semantic and
-    each value is the index of the accessor containing the attribute's data.
-    """
-    POSITION: Optional[int] = None
-    NORMAL: Optional[int] = None
-    TANGENT: Optional[int] = None
-    TEXCOORD_0: Optional[int] = None
-    TEXCOORD_1: Optional[int] = None
-    COLOR_0: Optional[int] = None
-    JOINTS_0: Optional[int] = None
-    WEIGHTS_0: Optional[int] = None
+    def __init__(
+        self,
+        POSITION=None,
+        NORMAL=None,
+        TANGENT=None,
+        TEXCOORD_0=None,
+        TEXCOORD_1=None,
+        COLOR_0: int = None,
+        JOINTS_0: int = None,
+        WEIGHTS_0=None,
+        *args,
+        **kwargs
+    ):
+        self.POSITION = POSITION
+        self.NORMAL = NORMAL
+        self.TANGENT = TANGENT
+        self.TEXCOORD_0 = TEXCOORD_0
+        self.TEXCOORD_1 = TEXCOORD_1
+        self.COLOR_0 = COLOR_0
+        self.JOINTS_0 = JOINTS_0
+        self.WEIGHTS_0 = WEIGHTS_0
+        for key, value in kwargs.items():
+            setattr(self, key, value)
+
+    def __repr__(self):
+        return self.__class__.__qualname__ + '(' + ', '.join([f"{f}={v}" for f, v in self.__dict__.items()]) + ')'
+
+    def to_json(self, *args, **kwargs):
+        data = copy.deepcopy(self.__dict__)
+        return json.dumps(data)
+
diff --git a/gltflib/models/gltf_model.py b/gltflib/models/gltf_model.py
index a1f1917..21bcedf 100644
--- a/gltflib/models/gltf_model.py
+++ b/gltflib/models/gltf_model.py
@@ -1,7 +1,8 @@
 import json
 from dataclasses import dataclass, asdict
 from dataclasses_json import DataClassJsonMixin
-from typing import List, Optional
+from dataclasses_json.core import _decode_dataclass
+from typing import List, Optional, Type
 from ..utils import del_none
 from .accessor import Accessor
 from .animation import Animation
@@ -18,6 +19,7 @@
 from .scene import Scene
 from .skin import Skin
 from .texture import Texture
+from .attributes import Attributes
 
 
 @dataclass
@@ -43,3 +45,37 @@ class GLTFModel(DataClassJsonMixin, BaseModel):
     def to_json(self, **kwargs):
         data = del_none(asdict(self))
         return json.dumps(data, **kwargs)
+    
+    @classmethod
+    def from_json(
+        cls: Type['GLTFModel'],
+        s: str,
+        *,
+        parse_float=None,
+        parse_int=None,
+        parse_constant=None,
+        infer_missing=False,
+        **kw
+    ) -> 'GLTFModel':
+        
+        init_kwargs = json.loads(
+            s,
+            parse_float=parse_float,
+            parse_int=parse_int,
+            parse_constant=parse_constant,
+            **kw
+        )
+
+        result = _decode_dataclass(cls, init_kwargs, infer_missing)
+        for mesh in result.meshes:
+            for primitive in mesh.primitives:
+                raw_attributes = primitive.attributes
+                if raw_attributes:
+                    attributes = Attributes(**raw_attributes)
+                    primitive.attributes = attributes
+
+                raw_targets = primitive.targets
+                if raw_targets:
+                    primitive.targets = [Attributes(**target) for target in raw_targets]
+
+        return result