add tests for attn head

Signed-off-by: Kyle Sayers <[email protected]>

Author: kylesayrs

src/compressed_tensors/quantization/quant_scheme.py

@@ -65,6 +65,7 @@ def validate_model_after(model: "QuantizationScheme") -> "QuantizationScheme":
                 QuantizationStrategy.TENSOR,
                 QuantizationStrategy.GROUP,
                 QuantizationStrategy.TENSOR_GROUP,
+                QuantizationStrategy.ATTN_HEAD,
             ):
                 if (
                     inputs.strategy == QuantizationStrategy.GROUP