fix signatures on model_validator functions (#314)

Signed-off-by: Brian Dellabetta <bdellabe@redhat.com>

Author: brian-dellabetta

src/compressed_tensors/quantization/quant_args.py

@@ -206,7 +206,7 @@ def validate_actorder(cls, value) -> Optional[ActivationOrdering]:
         return value
 
     @model_validator(mode="after")
-    def validate_model_after(model: "QuantizationArgs") -> Dict[str, Any]:
+    def validate_model_after(model: "QuantizationArgs") -> "QuantizationArgs":
         # extract user-passed values from dictionary
         strategy = model.strategy
         group_size = model.group_size

src/compressed_tensors/quantization/quant_scheme.py

@@ -48,7 +48,7 @@ class QuantizationScheme(BaseModel):
     output_activations: Optional[QuantizationArgs] = None
 
     @model_validator(mode="after")
-    def validate_model_after(model: "QuantizationArgs") -> Dict[str, Any]:
+    def validate_model_after(model: "QuantizationScheme") -> "QuantizationScheme":
         inputs = model.input_activations
         outputs = model.output_activations